Friday, October 26, 2018

The Origin of the Nikumaroro Sextant Box

When I started this blog I knew that I’d be writing about the origin of the Nikumaroro sextant box, but I didn’t think it would take me so long to get to it.  A brief review of what the Nikumaroro sextant box is and how it fits into the matter of the disappearance of Amelia Earhart’s is in order before I get to the main point of this post.

Amelia and her navigator, Fred Noonan, disappeared while attempting to fly across the Pacific Ocean in a Model 10E Lockheed Electra.  They took off from Lae, New Guinea on the morning of July 2, 1937, heading for tiny Howland Island, some 2500 miles away, and were never seen again. The group TIGHAR promotes the Nikumaroro Hypothesis — that having failed to find Howland, Earhart and Noonan landed the Electra on Gardner Island, now known as Nikumaroro, a then-uninhabited atoll located 400 miles to the southeast of Howland.  The Nikumaroro Hypothesis further supposes that a few days after Amelia landed the Electra on Nikumaroro’s fringing coral reef the plane was washed into the ocean and that Amelia and Fred died on Nikumaroro in the following weeks or months.

In support of the Nikumaroro Hypothesis, TIGHAR points to the story of the discovery of the remains of a castaway on Nikumaroro in 1940, not long after the island was settled by colonists from the British Gilbert and Ellice Islands Colony.  The settlement of Nikumaroro was carried out under the supervision of Gerald Gallagher, a British colonial official, in what was one of the final acts of expansion of the British Empire.  In September, 1940, Gerald Gallagher informed his superiors that the partial skeleton of a castaway had been found earlier in the year by a colonist work party, presumably while they were clearing vegetation for the planting of coconut palm trees.

Gallagher reported that searches of the vicinity of the castaway’s remains turned up several items, including a fragment of what he took to be a woman’s shoe and an empty sextant box marked with two four-digit serial numbers — 3500 and 1542.  Gallagher suggested to his superiors that the castaway might have been Amelia Earhart.  Gallagher’s superiors took this suggestion seriously and had the bones and items found near them sent to them for further analysis.  A doctor named David W. Hoodless, who taught at the Central Medical School in Fiji, examined the bones and concluded that the castaway had been a short, stocky male.  The sextant box was examined by Harold Gatty, a world-famous pioneer of air navigation who happened to be in Fiji. It is clear from Gatty’s remarks that he understood that he was being asked whether the sextant box could have come from Earhart’s Electra.  Gatty’s opinion was that the sextant box could not have been that of a navigation sextant used in modern aviation — ‘modern’ here meaning the late 1930s.  With the possibility of the castaway being Amelia Earhart ruled out, there was no further interest in determining the identity of the castaway.

In 1998 TIGHAR had Dr. Richard Jantz, a forensic anthropologist at the University of Tennessee, reanalyze the bones measurements made by Doctor Hoodless during his 1940 examination of the castaway’s bones (the castaway’s bones and the other items found nearby have long since disappeared).  Jantz cautiously concluded that the bones were ‘more likely female than male’ and were ‘more likely white than Polynesian or Pacific Islander’ [1].  This wasn’t exactly a resounding affirmation of the Nikumaroro Hypothesis, but TIGHAR made much of Jantz’s findings, sometimes neglecting to indicate the degree of uncertainty in Jantz’s conclusion.  In 2015 Pamela Cross of the University of Bradford and Richard Wright of the University of Sydney published a paper disputing Jantz’s conclusions, arguing that there was no reason to disbelieve Dr. Hoodless’s original conclusion that the castaway was a man [2].  In response to the Wright and Cross paper, Jantz conducted a new re-analysis of Dr. Hoodless’s notes, and this year published a paper that essentially concluding that there is a high probability that the castaway was Amelia Earhart [3].  I’m not a forensic anthropologist and the subject of this post is the Nikumaroro sextant box, so I will leave the question of whether the castaway was a short, stocky man or Amelia Earhart to those who by training are better qualified to address it.

So now onto the matter of the Nikumaroro sextant box.  The British colonial officials to whom Gallagher sent the sextant box understood that the four-digit numbers it was marked with might allow them to determine the box’s origin, but since they had determined that the castaway wasn’t Earhart this line of investigation was never pursued [4].  TIGHAR took up the challenge of using the serial numbers to trace the sextant box numbers to its owner.  It was eventually learned that the sextants used by the United States Navy in the early decades of the twentieth century are marked with two serial numbers.  One serial number is the sextants manufacturer, and the other is a serial number assigned by the U.S. Naval Observatory, which had the task of inspecting and maintaining the U.S. Navy’s sextants.

Brandis Sextant, Brandis Serial Number 3985

Same Sextant -- its Naval Observatory Serial Number

The boxes made to hold these sextants are marked with the manufacturer’s serial number of the sextant they originally held; some are also marked with the sextant’s Naval Observatory serial number.  The pair of numbers on the Nikumaroro sextant box, 3500 and 1542, match up well with serial number pairings on surviving examples of U.S. Navy sextants made by one particular sextant manufacturer, Brandis and Sons. If 3500 was a Brandis serial number and 1542 a Naval Observatory serial number, there was good reason to think that the Nikumaroro sextant box once held a Brandis sextant made for the U.S. Navy.  As discussed in my earlier posts on the Brandis serial number chronology, a Brandis sextant with serial number 3500 would have been made around the time of the First World War.

How could a World War One era Brandis nautical sextant box be connected to Amelia Earhart’s final flight?  TIGHAR proposed that the Nikumaroro sextant box once belonged to Fred Noonan, Amelia Earhart’s navigator.  Noonan had been a navigator on the Pan Am Clipper seaplanes that were the first to provide passenger air service across the Pacific Ocean. On those flights Noonan used a bubble octant, a kind of sextant made specifically for air navigation, to stay on course for the tiny islands that Pan Am Clippers would stop at to refuel when crossing the Pacific Ocean.  It is reasonable to think Noonan used a bubble octant to navigate Earhart’s Electra [5]. Bubble octants were quite unlike the nautical sextants that Brandis made during the First World War and so were the boxes used to store them.  When Harold Gatty remarked that the Nikumaroro sextant box could not have been used for modern air navigation, what he presumably meant was that the Nikumaroro sextant box was not made to hold a 1930s air navigation octant.

While Gatty’s remarks seem to rule out the possibility that the Nikumaroro sextant box was Noonan’s, TIGHAR points out that in a letter describing his navigational techniques while working for Pan Am, Noonan wrote: “Two sextants were carried – a Pioneer bubble octant and a mariner’s sextant. The former was used for all sights; the latter carried as a ‘preventer’ ”.  It is not clear what Noonan meant by ‘preventer’.  TIGHAR speculates that Noonan meant that he used a mariner’s sextant as a back-up for the Pioneer bubble octant that was his primary navigating instrument.  TIGHAR further suggests that Noonan’s mariner’s sextant was made by Brandis, offering as evidence a photograph of the navigator’s station of a 1930s Pan Am Clipper in which a box that looks like a Brandis nautical sextant box can be seen.  Since traditional nautical sextants were poorly suited for air navigation, TIGHAR further speculates that Noonan’s Brandis sextant had been modified into a Byrd sextant, an early version of an air navigation sextant; a sextant so modified would still fit in its original box.  TIGHAR further speculates that Noonan had his Brandis-Byrd sextant with him on the lost flight to Howland Island,  and that it is the box for this sextant that Harold Gatty passed judgement on in Fiji in 1940.

The case TIGHAR made for the Nikumaroro sextant box being Fred Noonan’s is a circumstantial one, but it nevertheless was plausible.  The big problem with it is that TIGHAR has never been able to prove that Fred Noonan actually owned a Brandis sextant, much less that he had one with him when he and Amelia Earhart disappeared on their way to Howland Island.

I began to follow TIGHAR in 2012, and the hypothesis that the Nikumaroro sextant box belonged to Fred Noonan was of particular interest to me.  At some a point an alternate hypothesis for the origin of Nikumaroro sextant box occurred to me.  In late 1939, only a few months before the castaway’s remains were found, the USS Bushnell, a U.S. Navy submarine tender outfitted as a hydrographic mapping vessel, visited Nikumaroro to survey the island and its lagoon.  My alternate hypothesis was that a Bushnell surveyor inadvertently left the box for the Brandis sextant somewhere in the vicinity of the castaway’s remains, where it was found a few months later in the search for the castaway’s personal effects.  Much of Nikumaroro is covered in forest and scrub and so it is conceivable that a Bushnell surveyor could have passed close to the castaway’s remains without seeing them.

Documents available on the TIGHAR website show that the Bushnell’s surveyors had set up a network of reference points throughout the island for the surveying work they were doing [6].  Some of that work involved measuring water depths from small boats making transects across the lagoon.  It occurred to me that the Bushnell surveyors might have determined their position when making these transects by using sextants to triangulate on the land-based reference points they had set up.  A hydrographic surveying manual published by the U.S. Coast and Geodetic Survey in 1931 confirmed that sextants were in fact used in this way [7].

So, sextants could have been used by the Bushnell surveyors on Nikumaroro, the boxes for those sextants could well have been marked with Brandis and Naval Observatory serial numbers, and a Brandis sextant box left on Nikumaroro by the Bushnell in late 1939 would have been there in time to be found after the discovery of the castaway in 1940.  When I offered up my alternate hypothesis on TIGHAR’s discussion forum, Ric Gillespie, TIGHAR's Executive Director, responded dismissively and with downright hostility, something he often did when a tenet of the Nikumaroro Hypothesis was in some way threatened. To give a sense of how that went I’ll mention that at one point, after I suggested that TIGHAR should search for records that might indicate whether a sextant with serial numbers 3500 or 1542 was issued to the Bushnell, Gillespie’s response was to say any such effort would be ‘wasting time on snipe hunts’; he also said that my hypothesis was ‘thoroughly bizarre’ and that I should ‘go do some real research’ [8]. In the rest of this post, I’ll discuss what Ric might have learned had he spent a few afternoons researching the USS Bushnell at the National Archives in Washington, D.C., a two-hour trip from his home.

My first National Archives trip was in December of 2016. If the Bushnell’s surveyors had used sextants to determine position while surveying Nikumaroro’s lagoon, I had reason to think that they would have recorded the serial numbers of the sextants they used.  The 1931 U.S. Coast and Geodetic Survey’s Hydrographic Survey Manual showed an example of a data sheet for a hydrographic survey on which serial numbers of the sextants that were used are recorded (see photo below).  My goal was to find if something like those data sheets existed for the Bushnell survey of Nikumaroro.

U.S. Coast & Geodetic Hydrographic Survey Data Sheet

My first day was spent at the National Archives and Record Administration (NARA) facility in Suitland, Maryland.  I knew that Suitland was a repository for maps produced by the U.S. Navy and so it seemed like a good place to look for the Bushnell’s field surveying  records if they still existed. At Suitland I was able to find rough maps of the water depths of Nikumaroro’s lagoon that were produced while the Bushnell was still at Nikumaroro.  The raw data from which these maps were prepared were not at Suitland, however.  On the shelves of the Suitland reference room I found a decades-old finding aid for the records of the Bushnell’s hydrographic surveying work.  The finding aid showed that the maps I found at Suitland and notebooks containing the data from which those maps were prepared were at one time kept together somewhere in a single collection. That collection had long since been broken up and the maps eventually ended up at Suitland.  I was told that if the field notebooks for Nikumaroro still existed, they would be at the NARA archive in downtown Washington, D.C.  The Suitland staff member I spoke with held out little hope that those notebooks would still exist.

At the National Archives in Washington the next day I had the good fortune of meeting Chris Killillay, a NARA staff member who has a deep knowledge of the U.S. Navy material held in the archives.  I didn’t have file reference numbers that would help him figure out if the field notebooks I was looking for still existed, or where in the voluminous collection of U.S. Navy material held by NARA those notebooks might be.  Mr. Killillay nevertheless had some ideas about where to look, and after disappearing into the file storage area for a while he came back out and told me that he had found the Bushnell’s field notebooks for Nikumaroro.  I was gobsmacked. I filled out a request form to have the notebooks delivered to the NARA reading room and a little while later up in the reading room a cart came out to me loaded with box after box of Bushnell surveying notebooks, and not only for Nikumaroro but for many other islands that the Bushnell surveyed during its 1939-1940 surveying season.

It was amazing to have the Bushnell’s surveying notebooks sitting in front of me on a cart.  I was probably the first person to ask for them in 70 years.  I located the notebooks for Gardner Island and started to look through them.  Inside there were pairs of preprinted pages on which the measurements needed for map construction were recorded. The photo below shows part of a typical two-page spread.  On the left page are water depth measurements and the times at which the measurements were made, and on the right page are measurements of two angles, indicated as ‘left’ and ‘right’, made on three reference points, indicated as GAR, GUN, and WIT.  The left angle was presumably that between reference points GAR and GUN, and the right angle that between GUN and WIT.  At the end of a series of measurements on some notebook pages the words ‘sextants check’ were written, as can be seen in the second photo below.

Notebook Pages from the Hydrographic Survey of the Nikumaro (a.k.a. Gardner Island) Lagoon

'Sextants Check' on a Notebook Page

 Clearly, sextants had been used in surveying Nikumaroro. But much to my disappointment I was unable to find sextant serial numbers in any of the notebooks I looked through, either for Nikumaroro or for any other island that the Bushnell visited during that same surveying season. I didn’t have time to look through every page of every notebook but I had looked through enough of them to think it unlikely that sextant serial numbers were recorded in any of the notebooks.  Apparently it was considered unnecessary to indicate the specific instruments used to make the measurements recorded in these notebooks. Rather than continue to look through the Bushnell’s notebooks for the 1939-1940 surveying season, I used the remaining time I had at the Archives to look at notebooks for the 1938-1939 season, during which the Bushnell conducted hydrographic surveys along the Caribbean coast of South America.  I managed to find a notebook page that contained the entry ‘Sextant #2806 & #2810 checked’ (see photo below). Here were sextants with four-digit numbers, but the numbers weren’t 3500 or 1542, and it wasn’t clear whether 2806 and 2810 were Naval Observatory numbers or manufacturer’s serial numbers.  I looked through other notebooks like the one in which the 2806 and 2810 appeared, but all of them were devoid of sextant serial numbers.

Sextant Numbers on a Page from the Bushnell Survey of the Coast of Venezuela

That was pretty much as far as I got on my first NARA visit.  The upshot was that I found documentary evidence that Bushnell surveyors used sextants in their hydrographic survey of Nikumaroro, but there was no proof that those sextants were Brandis sextants, much less that one of them was Brandis #3500, USNO #1542.

My next NARA trip occurred in August of this year.  A few months earlier a person named Lew Toulmin wrote a report about the findings of his research into the origins of the Nikumaroro Sextant box [9], which included research at the National Archives in Washington, D.C.  Toulmin examined an index card catalog for NARA’s holdings of U.S. Naval Observatory’s correspondence for the period 1909-1925.  The card catalog was organized by subject, and one of those subjects was sextants.  Each card gave a terse summary of correspondence in a Naval Observatory file and a file number that could be used to locate the actual correspondence.  Toulmin found nothing on the cards he looked through that allowed him to determine the origin of the Nikumaroro sextant box. On this Archives trip I wanted to have a look at the 1909-1925 card catalog that Toumlin had already looked through, because I thought it would point me to Naval Observatory correspondence that would allow me to refine the Brandis serial number chronology that I’ve discussed in earlier posts.  But I was also interested in a second card catalog that Toulmin hadn’t looked at, which was for NARA’s holdings of U.S. Naval Observatory correspondence for the period 1925-1943.  My thought was that the Naval Observatory, in its role as the U.S. Navy’s sextant service shop, might have supplied the Bushnell with Brandis sextants, and the 1925-1943 card catalog might point me to documents attesting to this. 

As I started to go through the index card catalogs in NARA’s reading room I quickly realized what a daunting task it was to glean information from them. There were a huge number of index cards on the subject of sextants and many of the cards were handwritten in a nearly illegible script. It was impossible to digest the information on the 1909-1925 index cards while sitting in the NARA reading room, so all I could do was photograph them so that I could decipher them when I got home. The 1925-1943 card catalog was easier to read, but I only found two index cards under the subject of sextants that seemed to have potentially promising leads. The first card read:

Sextants, patrol Bt. Brandeis - unfit for use - 144 turned in to N. Obvy - Supt. N. Acad. 1/14/37 - 2-2X3.

Brandeis’ was obviously a misspelling of Brandis, and I recognized ‘Sextants, patrol Bt.’ to be a reference to the 5-inch radius Brandis sextant that I wrote about in the post titled ‘Brandis Sextant Taxonomy, Part Five’. All the Brandis sextants of this type that I knew of had Brandis serial numbers in the 3000s, not far off from the presumed Brandis serial number on the Nikumaroro sextant box. Perhaps the full Naval Academy memo this card summarized actually listed the serial numbers of the Brandis patrol boat sextants that were turned into the Naval Observatory.  In Brandis Sextant Taxonomy, Part Five I noted that sextants of this type had features that made them well-suited for hydrographic surveying.  So when I saw this index card I wondered if the sextants were refurbished at the Naval Observatory and sent to the USS Bushnell. The Naval Academy letter was dated January 14, 1937, so there would have been enough time to get those sextants fixed and to the Bushnell in time for the voyage on which the Bushnell surveyed Nikumaroro.

The second index card read:

U.S.S. Bushnell - 1004 - Rq. for sextant mirrors - 24 Index + 24 Horizontal - C.O. 8/4/38. 2200.
6105  Yr. 1004 2200 Shipped this date P.P. Navobsy. Inv. 290 — To C.O. 8/5/38   1500

There was no mention of sextants in the terse summary written on this index card, but I wondered if the full message that the card summarized might say something about sextants.  By the time I found these two cards it was too late in the day to have the files for this correspondence retrieved.  My visit to the Archives had come to an end, and so I would have to come back another time to follow up on the two index cards.

It wasn’t until last week that I was able to return to the Archives and access the files that the cards referred to. I was disappointed to find that the full Naval Academy letter summarized on the first card said nothing about the serial numbers of the Brandis patrol boat sextants sent to the Naval Observatory.  The correspondence on the second card also led nowhere; what was written on the card was basically the full extent of the correspondence, which apparently had occurred by telegram or radio.

The information on those two index cards led me nowhere; I had reached a dead end. Was there anywhere else in the Archives left to search? The two disappointing index cards were filed under the subject ‘Sextants’ in the card catalog, and I remembered that further along in the card catalog were cards filed under the subject ‘Surveying Instruments’.  I went back through those index cards and found a few cards summarizing correspondence between the USS Bushnell and the Naval Observatory.  The card in the photo below was particularly tantalizing.  It summarized a chain of correspondence between the Bushnell and the Naval Observatory about surveying instruments that the Bushnell had sent to the Naval Observatory for repair in late 1938.  I put in a request for the files for this correspondence, but the file boxes that came to up to me in the NARA reading room didn’t contain the corrspondence I was looking for.  Chris Killillay was on duty when I went downstairs to the room where NARA archives specialists meet with researchers, and I told him that I had been unable to find the correspondence I wanted.  He went into the file storage area for a while, and when he came out he helped me fill out a request form for a file box that he thought was the only one left in the Archives that might hold the correspondence I wanted.

Index Card from the USNO Correspondence 1925-1943 Card Catalog

When that file box came to me in the NARA reading room I quickly saw that it contained the correspondence I wanted to see.  I found a memo to the Naval Observatory written by the commanding officer of the Bushnell in October of 1938 stating that the Bushnell would be sending surveying instruments to the Naval Observatory for repair; nineteen sextants were among the instruments to be sent. The Bushnell's C.O. was giving the Naval Observatory advanced notice because he wanted to make sure he got those instrument back in time for his next hydrographic survey cruise.  No serial numbers or manufacturer’s names were given for the sextants or for any of the other listed instruments.

A little further into the chain of correspondence I came upon a four page memo from the Bushnell dated November 15, 1938, listing each instrument to be sent to the Naval Observatory and the specific work that needed to be done.  The first two pages of this memo are reproduced below.  Item 12 on the list is 'Sextant, Brandis N.O. 1542  General Overhaul'.  A note penciled into the margin indicates that this sextant was returned to the Bushnell on January 17, 1939.  The ’N.O.’ is obviously an abbreviation for Naval Observatory [10].  So here in this memo it is documented that a Brandis sextant with U.S. Naval Observatory number 1542 belonging to the USS Bushnell was refurbished by Naval Observatory in late 1938 and was back aboard the Bushnell by January of 1939, about a year and a half after Amelia Earhart and Fred Noonan went missing, and about a year before the Bushnell stopped at Nikumaroro to survey it.  The sextant box found on Nikumaroro marked with the numbers 3500 and 1542 wasn’t Fred Noonan’s, it was a Brandis sextant box that a Bushnell surveyor happened to lose in the vicinity of the remains of the castaway’s final campsite.

List of Items Shipped from the Bushnell to the Naval Observatory, Page 1

List of Items Shipped from the Bushnell to the Naval Observatory, Page 2

Marginal Note on Page 2 Indicates Items 11 through 15 Returned to the Bushnell on 1-17-39

Comments, corrections, additional relevant facts, differing viewpoints, etc., are always welcome.  Send to

[1] Amelia Earhart’s  Bones and Shoes? Current Anthropological Perspectives on an Historical Mystery.  This report was ‘prepared for release’ at the 1998 annual convention of the American Anthropological Association. It can be downloaded at the TIGHAR website:

[2] The Nikumaroro Bones Identification Controversy: First-hand examination versus evaluation by proxy - Amelia Earhart found or still missing? Pamela J. Cross and Richard Wright. Journal of Archeological Science: Reports 3 (2015) 52-59.

[3] Amelia Earhart and the Nikumaroro Bones: A 1941 Analysis versus Modern Quantitative Techniques. Richard L. Jantz.  Forensic Anthropology Vol. 1, No. 2: 83–98

[4] Actually, at this point the colonial officials thought that a sextant with the numbers 3500 and 1542 had been found, not just an empty sextant box, but the idea is the same.

[5] Noonan borrowed a Pioneer aviation bubble octant from the U.S. Navy.  The signed receipt indicates it was to be used on the round the world flight with Amelia Earhart.  A copy of that receipt can be found at:

[6] Tighar’s collection of Bushnell documents is available for download at:

[7] Hydrographic Manual, U.S. Coast and Geodetic Survey Special Publication No. 143.  J.H. Hawley. U.S. Government Printing Office, Washington, D.C. (1931)

[8]  My quotes come from Replies 40, 41 and 121 on the Seven Site Thread  of the TIGHAR discussion forum (,508.0.html). There were other insulting remarks and a strange degree of obtuseness about my hypothesis from Gillespie and some of his loyal followers. 

[9] Toulmin’s report is titled: SEXTANTS AND NOONAN/EARHART: The Pensacola Fred Noonan Sextant and Box and the Amelia Earhart—Fred Noonan Disappearance and Sextant Research on the US Naval Observatory at the US National Archives.  It is dated May, 2018.  Mr. Toulmin’s report will be published on his website,, on the page on Finding Lost Airplanes.  Until then it is available  upon request at 

[10] We can be sure that 1542 was the sextant’s Naval Observatory number, not its Brandis serial number by looking at item 8, a Keuffel and Esser protractor, for which both the manufacturer’s number, K&E #10013, and Naval Observatory number N.O. #176, are given.

Friday, May 25, 2018

Brandis Sextant Taxonomy, Part Seven: Outlier Sextants

Several Brandis sextants I’ve come across aren’t like of any of the five sextant types I’ve discussed in previous posts.  One of these outliers is a sextant with Brandis serial number 5687 (Figure 1).  Brandis 5687’s frame has one straight and one curved lateral brace connecting its radial arms, like the U.S. Navy Surveying Sextant illustrated in Brandis Catalog No. 20 (Figure 2).  Because of its frame pattern, I initially thought that Brandis 5687 was a surveying sextant but then I noticed that its arc scale is graduated in 10-minute intervals (Figure 3).  U.S. Navy surveying sextant specifications published in 1897, 1901, and 1918 require the arc scales of surveying sextants made for the Navy to be graduated in 20-minute intervals, so Brandis 5687 isn’t a surveying sextant, at least not according to these specifications.

Figure 1.  Brandis 5687

Figure 2. Brandis Catalog No. 20

Figure 3.  Brandis 5687's Arc Scale
Brandis 5687 was the first sextant of its type that I came upon, but eventually I found two more like it; their Brandis serial numbers are 5965 and 6028, respectively.  I came upon all three of these sextants on eBay, and so all I know about them is what I can see in the photos posted in their eBay listings and what little their sellers had to say about them.  As far as I can tell, none of these sextants are marked with a Naval Observatory serial number but it may be that the photos provided in their eBay listings don’t happen to show them.  I’ll note here that the eBay listing for Brandis 5965 reported its box to have dimensions of 10” x 10” x 5.5”, which matches the dimensions of Brandis surveying sextant boxes.  That tells me that sextants of this type have the same frame radius, 6 inches, as a Brandis surveying sextant.

The U.S. Navy’s high grade sextant specifications published in 1897 requires the arc scales of high grade sextants to be graduated in 10-minute intervals. Brandis 5687 meets this requirement, but it fails to meet an additional requirement in these specifications that high grade sextants have at least two curved lateral braces connecting their radial arms. The frame pattern of Brandis 2864 (Figure 4), which was discussed in my earlier post on Brandis high grade sextants, conforms with this specification as does the frame pattern of the high grade sextant illustrated in Brandis Catalog No. 20 (Figure 2).

Figure 4. Brandis 2864

So far we’ve looked at how Brandis 5687’s frame and arc scale compare to those of Brandis surveying sextant and high grade sextants. Let’s next look at how Brandis 5687’s tangent screw compares to the tangent screws that sextants of these two types are fitted with.  The U.S. Navy’s surveying sextant specifications published in 1901 requires surveying sextants to have a 2.75-inch long, two-headed tangent screw, while the Navy’s specifications for high grade sextants published in 1897 requires high grade sextants to have a 4.1-inch long, single-headed tangent screw.  The surveying and high grade sextants illustrated in Brandis Catalog No. 20 (Figure 5) appear to be fitted with the tangent screws called for in these specifications, so it seems that the Navy sextant specifications in effect when Brandis Catalog No. 20 was published called for the same kind of tangent screws that the earlier specifications did.  What kind of tangent screw is Brandis 5687 fitted with? The photo in Figure 1 shows us that it has a short, two-headed tangent screw. Photos I have of Brandis 5965 and Brandis 6028 show that they too, are fitted with a short, two-headed tangent screw.

Figure 5  Tangent Screws, Brandis Catalog No. 20

As a final point of comparison, let’s consider how Brandis 5687’s sighting devices compare to those of Brandis surveying and high grade sextants.  Both the U.S. Navy’s surveying sextant specifications published in 1901 and its high grade sextant specifications published in 1897 require instrument manufacturers to furnish these sextants with a sighting tube, short telescope, and long telescope.  These three devices can be seen in the illustration of the surveying in Brandis Catalog No. 20.  They also can be seen in the illustration of the high grade sextant in Brandis Catalog No. 20, but an additional device appears in this illustration as well.  That additional device is a second eyepiece for the high grade sextant’s long telescope.  The Navy’s 1901 surveying sextant specifications requires a surveying sextant’s long telescope to be furnished with an eyepiece providing a magnification of six diameters, while the Navy’s 1897 high grade sextant specifications require the long telescope of a high grade sextant to be furnished with two eyepieces providing magnifications of six and twelve diameters, respectively. Apparently, the sextant specifications in effect when Brandis Catalog No. 20 was published were the same as these earlier specifications with respect to the sighting devices these two sextant types were to be provided with.  A photo of the sighting tube, short telescope, long telescope, and second eyepiece for the long telescope of a high grade sextant, in this case the high grade sextant Brandis 2864, can be seen in Figure 6.  The way these four devices are stored in Brandis 2864’s box can be seen in Figure 7.  The holder for the long telescope is at the bottom right of the box, while the holder for the sighting tube, short telescope, and long telescope is at the box’s rear right corner.  In the photo in Figure 8 of Brandis 5687 in its box, a sighting tube, short telescope and long telescope, can be seen but not a second eyepiece for the long telescope.  We can be sure that the photographer didn’t neglect to include a second eyepiece in this photo, because this photo shows that the holder in the corner of Brandis 5687’s box doesn't have a space to hold such a thing.  So Brandis 5687’s long telescope has only one eyepiece, and in this respect Brandis 5687 is like a surveying sextant. Photos that I have of Brandis 5965 and Brandis 6028 show that their long telescopes, too, were supplied with only one eyepiece.

                                                     Figure 6. Brandis 2864 Sighting Devices (l to r):                                                                    Second Eyepiece for Long Telescope, Sighting Tube, Short Telescope, Long Telescope.

Figure 7.  Brandis 2864 Box with Sighting Devices in their Holders

Figure 8. Brandis 5687 in its Box, with Sighting Devices

Brandis 5687 and other sextants of its type are like Brandis surveying sextants in terms of their frame pattern, tangent screw, and the sighting devices with which they were provided, but their arc scales are graduated like the arc scales of Brandis high grade sextants. Sextants like Brandis 5687 don’t appear in any Brandis product literature I’ve seen and so I don’t know what name Brandis had for them  Until I have a better idea what sextants like Brandis 5687 were called, I’ll refer to them as ‘Type 6 sextants’, simply because they are the sixth type of sextant I’ve discussed.

A photo of second type of outlier sextant that I’ve come across appears in Figure 9.  Its Brandis serial number is 5981 and it is also marked with U.S. Naval Observatory serial number 1142.  What sets Brandis 5981 apart from the sextants discussed in previous posts is that its frame has three curved lateral braces connecting its radial arms.  Brandis 5981’s arc scale is marked in 10-minute increments, like the arc scale of a high grade sextant.  Brandis 5981’s frame pattern is different than the high grade sextant depicted in Brandis Catalog No. 20, but it nevertheless conforms with the U.S. Navy’s 1897 high grade sextant specifications, which requires high grade sextant frames to have at least two lateral braces.  Brandis 5981’s tangent screw is long and single-headed as required by these specifications, and its long telescope has two eyepieces, which also meets the requirements in these specifications.
Figure 9 Brandis 5981
As was the case for the Type 6 sextants, I don’t have any Brandis product literature that indicates the name Brandis had for sextants of this type. A partial scrap of the U.S. Naval Observatory inspection certificate inside the lid of Brandis 5981's box is not legible in the photo I have of it, which is unfortunate, because that certificate might have told us what the U.S. Navy called sextants like it [1].  Until I find something that tells me what sextants like Brandis 5981 were called, I’ll unimaginatively refer to them as Type 7 sextants.

Brandis 5981 isn’t the only Type 7 sextant I’ve come across.  Another sextant of this type has Brandis serial number 5851 and is marked with U.S. Naval Observatory number 1110.  Brandis 5981 and Brandis 5851 have some of the highest Brandis serial numbers I’ve seen, yet their Naval Observatory serial numbers are lower than most Brandis sextants I’ve seen.  That is something that is worth further discussion, but I’ll save that discussion for some future post.

Once I became aware of the existence of Type 7 sextants I realized that I’d seen a photo of a Brandis sextant frame with three curved lateral braces in Bill Morris’s book, The Nautical Sextant.  The frame, separated from the rest of the sextant, appears on a page comparing the similarly detached frames of sextants from several different manufacturers.  I contacted Mr. Morris to learn more about this sextant, thinking it was another Type 7 sextant.  What he told me about this sextant, whose Brandis serial number 5191, suggests that it is yet another type of Brandis sextant.  Mr. Morris reports that Brandis 5191’s vernier scale is graduated to provide a 30-second reading precision.  As we’ve seen, the arc scales of Type 7 sextants are graduated in 10-minute intervals.  In my experience looking at Brandis and other sextants, I’ve pretty consistently found that sextants with vernier scales providing a 10-second reading precision have arc scales graduated in 10-minute intervals, and sextants with vernier scales providing a 30-minute reading precision have arc scales graduated in 20-minute intervals.  The U.S. Navy sextant specifications referred to earlier in this post in fact require these particular pairings of vernier scale reading precisions with arc scale graduations. The 1901 surveying sextant specifications require an arc scale graduated in 20-minute intervals and a vernier scale providing a 30-second reading precision, while the 1897 high grade sextant specifications required an arc scale graduated in 10-minute intervals and a vernier scale providing a 10-second reading precision.  The 30-second reading precision of Brandis 5191’s vernier scale suggests to me that Brandis 5191’s arc scale is graduated in 20-minute intervals, and so I’m tentatively taking Brandis 5191 to be an example of yet another Brandis sextant type, which I will refer to as a Type 8 sextant.  I will reach out to Mr. Morris and ask him specifically how Brandis 5191’s arc sale is graduated and what kind of tangent screw it is fitted with.  As of this post’s publication date, I’ve seen no other sextant like Brandis 5191, so it is an outlier even among the outlier Brandis sextant types discussed in this post.

This was a difficult post to write.  I didn’t report every bit of information that I have about these different sextant types or fully flesh out my assumptions because to do so would have required digressions that I felt were too lengthy.  Classifying these outlier sextants as belonging to three types distinctly different from each other and from the sextant types discussed in earlier posts was a useful way to organize my discussion of them, but it may not be the way people classified them back when Brandis was making them.  For instance, it could be that what I’ve categorized as a Type 7 sextant was simply a later, beefed-up version of the U.S. Navy High Grade sextant featured in Brandis Catalog No. 20.  If and when any new information comes in about any of these outlier sextant types that helps to better understand them, I will update this post or write a post to update what appears here.

Comments, corrections, additional relevant facts, differing viewpoints, etc., are always welcome.  Send to
[1]  Naval Observatory inspection certificates have a line where the sextant’s type was usually, but not always, been entered. 

Sunday, January 7, 2018

The Mystery of the RO Numbers

In my research on the origins of the Nikumaroro sextant box, I’ve come across dozens of sextants that were made for the U.S. Navy and inspected at the U.S. Naval Observatory in the early decades of the 20th century.  These sextants can be recognized by the Naval Observatory serial numbers scratched into their limbs.  The Naval Observatory serial numbers I’ve seen on these sextants are four digits long or less and are invariably preceded by the Naval Observatory 'NO' hallmark, i.e., the letter ‘N’ inscribed in the letter ‘O’.  All the sextants marked in this way were made by American manufacturers, and while most of them were made by Brandis and Sons, I’ve also seen sextants made by three other companies, Keuffel & Esser, Buff & Buff, and Stackpole & Brother, and a very old sextant box that originally held a Warner & Swasey sextant [1].  The boxes for many of these sextants contain a certificate prepared by the U.S. Naval Observatory providing corrections to apply for small angular measurement biases specific to each sextant.

A Typical Naval Obsevatory 'NO' Marking

A Naval Observatory Inspection Certificate

Five sextants that I’ve seen have markings that indicate that they were once in the U.S. Navy’s possession and that they were inspected at the Naval Observatory, but they are distinctly different from the sextants I’ve just described.  One sextant's frame has a bell-like outline, within which there are three circular rings abutting arranged in a triangular pattern.  Neatly inscribed in its limb is ‘Cairns, 12 Waterloo Road, Liverpool’; ‘Cairns’ apparently refers to Alexander Cairns, a instrument dealer in Liverpool, England, during the third quarter of the 19th century [2].  Scratched into the limb is ‘US Navy’ followed by an ‘R’ inscribed in an ‘O’ and then the number 11317.

Cairns Sextant Limb Markings

Another sextant is in the New Bedford Whaling Museum’s collection, donated by the family of a late 19th century New Bedford whaling captain named Daniel W. Gifford.  A museum catalog indicates that the limb is marked ‘Spenser, Browning & Co London’, ‘US Navy’, and the ‘RO’ symbol followed by the number 16977 [3].  Spenser, Browning & Company was a navigational instrument maker in London, England, in the middle decades of the 19th century [4].

The Captain Gifford Sextant

A third sextant, also made by Spenser, Browning & Co., appeared in the online catalog of an antiques dealer [5].  The inside of the sextant’s box lid is marked ‘Paris Exhibition 1867, George Davidson, U.S. Coast and Geodetic Survey Philadelphia, Pa’.  It has a 10-inch radius frame, and the catalog listing indicates that it is marked “U.S. Navy 30183”.  A close-up view of the limb in a catalog photo is not sharp, but I can see that the number 30183 is preceded by the Naval Observatory ‘NO’ hallmark and followed by an ‘RO’ symbol.

George Davidson U.S. C&G.S. Sextant

A fourth sextant, which is currently listed as for sale in the online catalog of another antiques dealer [6], has 'Captain Walton O. Hooker Jr Gardiner Maine Ship “Harry Morse" 1878' marked in script on its index arm and on a plate on the the sextant’s box.  The catalog listing indicates that the limb is marked 'E. Loueux a Paris (2266)  Schiaveni Bellieni a Bresl', and 'US Navy R31518'; a close-up view of the limb reveals the latter marking to be US Navy followed by an ‘RO’ symbol and the number 31518.  Attached to the inside of this sextant’s box lid is a U.S. Navy inspection certificate dated October 10, 1918, indicating that it was classified as a high grade sextant.  I have found nothing confirming that a sextant maker or dealer of by name Loueux existed, and so I’ve wondered if this sextant was actually made by Lorieux, a French instrument maker in the 19th century.

Captain Hooker Sextant and Box

Box Handle Anchor Plate, Captain Hooker Sextant

Limb Markings on the Captain Hooker Sextant

The fifth sextant is an octant with an eight-inch radius brass frame with an ivory arc scale that was listed in an online auction held in 2010 [7].  The octant is described as being marked ‘US Navy 13126’, and the box that holds it is said to contain a label for D. Eggert & Son, a marine chronometer maker and seller of nautical instruments in 19th century New York City [8].  From what little I know of D. Eggert & Son, they were not sextant makers, thus it is unclear who this sextant’s manufacturer was. The auction listing does not mention an ‘RO’ symbol, but I think it likely based on the examples of the four previous sextants that an ‘RO’ symbol  precedes the ‘13126’.

D. Eggert & Son Sextant

I didn’t doubt that the markings scratched into the limbs of these five sextant were put there by the U.S. Naval Observatory, but why were they different than the usual Naval Observatory markings?  What was the ‘RO’ symbol in place of the usual Naval Observatory hallmark meant to signify, and why were the serial numbers following the ‘RO’ symbol five digits long, not four digits or less?

The five sextants were not only different in terms of how the Naval Observatory marked them, they were very different kinds of sextants than the ones the U.S. Navy typically acquired in the early 20th century.  At least four of the five sextants were made by non- U.S. sextant makers, and the frame radius and bracing pattern of several of them don’t conform with the U.S. Navy sextant specifications.  All five sextants appear to have been made in the 19th century and so they are older than any of the sextants whose limbs are marked with NO serial numbers.  Several of them appear to have been in the possession of private citizens (the Captain Gifford and Captain Hooker sextants) or a civilian government entity (the George Davidson Coast & Geodetic Survey sextant).  Many sextants with the usual ‘NO’ number markings ended up in the hands of private citizens or civilian organizations after they left U.S. Navy service, but it seemed quite possible that these three sextants were used by civilians before they entered U.S. Navy service.  So, my guess was that the OR serial number system was used by the U.S. Navy to track non-standard sextants that it had acquired in some way other than its usual acquisition process, which I understand to have been to purchase sextants made to U.S. Navy specifications from the manufacturer that offered them at the best price through a competitive bidding process [9].

At first I had no idea how or why the Navy might have come to possess these five sextants, but then I remembered something I had read about in the Annual Reports of the U.S. Naval Observatory.  When the United States entered into the First World War, U.S. manufacturers were unable to meet the demand for many kinds of nautical instruments needed by the Navy and merchant marine fleet.  U.S. Navy Assistant Secretary Franklin Delano Roosevelt therefore led a campaign to solicit the public for donations of nautical equipment [10].  The campaign was publicized with Eyes for the Navy posters like the one below, which emphasized the need for binoculars and spyglasses to help the crews of naval vessels and merchant ships look for German submarines.

Eyes For the Navy Poster

Binoculars and spyglasses were not the only kinds of equipment the Navy asked the public to donate, however.  An organization called The Four Minute Men, which sent speakers into theaters throughout the country to give short speeches urging the public to donate nautical equipment to the Navy.  An internal memo circulated by the organization to help its members prepare their speeches contains a statement from the Navy about what equipment was needed and how donated items would be handled [11]:

"Send your binoculars, spyglasses, and telescopes by parcel post or express to Franklin D. Roosevelt, Assistant Secretary of the Navy, care of Naval Observatory, Washington, D. C. (Sextants and chronometers are also urgently needed). On the outside of the package write your name and address. On the inside, tie a tag on the instrument, again giving your name and address.
Immediately upon receipt you will get a letter from the Naval Observatory, stating that a test will be made.

Instruments are tested as soon as possible and those not suitable are returned to the sender. So far, only 5 per cent have been found unsuitable. Instruments somewhat out of repair will be accepted as there is a repair department in the Naval Observatory. A glass with a slight chip may pass the test, but the glasses must be of a good grade.

Upon acceptance of the glass, sextant or chronometer, you will be sent a letter of thanks, signed by Franklin D. Roosevelt, Assistant Secretary of the Navy. A check for $1 will be sent you, which sum will constitute the rental price, or in event of loss, the purchase price of the article.

The instrument is then entered in the records at the Naval Observatory with your name, address, and key number. A metal tag with your name and address is securely attached by wire to the instrument and, as an additional safeguard, your key number is engraved on the inside of the instrument. The instruments are then shipped in lots and distributed among the commandants who in turn distribute them, taking a receipt for each instrument, just as is done with all other Navy property.

While it is, of course, impossible to guarantee your glass, sextant or chronometer, against damage or loss, every precaution has been taken for its return at the close of the war. The only precaution the sender needs to take is to notify the Naval Observatory of any change of address, or to see that mail being sent to the old address will be properly forwarded at the close of the war."

Things to note here are that sextants were among the items that the public was being asked to donate; that donated items were sent to Franklin D. Roosevelt, c/o the U.S. Naval Observatory, where they were inspected for usability; and, that Naval Observatory engraved a ‘key number’ on equipment accepted for use.  It’s tempting to think that the ‘R’ in the ‘RO’ symbol on the five sextants signifies that they were donated by civilians through the program led by a man whose last name begins with the letter ‘R’; the Naval Observatory’s Annual Report for Fiscal Year 1919 refers to the donated equipment as “Roosevelt Glasses”, which suggests that at the Naval Observatory, Roosevelt was very much associated with the donated equipment.  The Fiscal Year 1919 Annual Report states that some 52,000 donated binocular and spyglasses had been received and inspected at the Naval Observatory, of which some 32,000 had been accepted for use.  A serial number series extending to five digits would have been needed to track that number of donated equipment [12].

In another part of the memo, the organization’s director wrote the following about what the Eyes for the Navy campaign had already achieved by the February, 1918 date of the memo:

Many remarkable binoculars, spyglasses, telescopes, chronometers, and sextants have been received. Among these are many that have historic interest dating back to the Spanish, Civil, and Mexican Wars, even the War of 1812, and a few from the Revolution— these glasses have already done their bit. They are coming to the Navy now for use in this greatest of all wars; they are coming from men of science, from travelers, from sportsmen, from men who have had a good glass lying idle for years and years.

Who will want to keep a glass for a little selfish amusement when it can serve such a serious and such a great purpose? Who will dare appear in public with a glass, after the Navy needs are known.

Wm. McCormick Blair, Director, Four Minute Men

This confirms that sextants were indeed among the items the U.S. Navy received through the Eyes for the Navy program.  Perhaps the Gifford, Hooker, and Davidson sextants were the kind of things Blair was referring to in his comment on the age and historical interest of some of the donated nautical equipment.
So, a pretty strong circumstantial case can be built around the idea that the five sextants were donated to the U.S. Navy through the Eyes for the Navy campaign.  This idea provides a plausible explanation for the NR symbols and the five-digit serial numbers they are marked with, and why the Navy had in its possession sextants that weren’t American-made to U.S. Navy specifications (i.e., civilians were under no obligation to buy sextants made to government specifications).  What I had missed until a couple of weeks ago was that I had in my possession a piece of evidence that makes this case rather definitive.  While trying to put my collection of sextant photos into better order, I happened to take a look at a photo of the side of the box for the George Davidson sextant displayed at the Paris Exhibition of 1867.  That photo,reproduced below, shows a shipping label indicating that the box was sent by T.D. Davidson of San Francisco, California to  ‘Hon. F.D. Roosevelt, Naval Observatory, Washington D.C.’, i.e., the address to which the Eyes for the Navy campaign instructed the public to send donated nautical equipment.

Shipping Label on the George Davidson Sextant Box

Comments, corrections, additional relevant facts, differing viewpoints, etc., are always welcome.  Send to
[1] A photo of this sextant box can be seen at the TIGHAR web site.  Go to  I suspect that this sextant box may date to the very late 19th century.
[2] This according to the catalog description of a very similar-looking sextant in the Smithsonian Museum’s Behring collection.  See:
[3] The New Bedford Whaling Museum’s online catalog of its holdings can be found at:
The RO symbol is described as a registered trademark symbol in a museum catalog pdf file I downloded at:
[4] This according to a web page of the Smithsonian Museum’s Behring Center:  Earlier and later in the 19th century, Spencer, Browning & Co operated under similar names.
[5]  Skinner Auctions online catalog:
[6] Rock Island Auction Company online catalog:
[7] Skinner Auction online catalog:
[8] A history of the firm Eggert & Son can be found on pages 375-376 of: Marine Chronometers at Greenwich: A Catalogue of Marine Chronometers at the National Maritime Museum, Greenwich (Oxford University Press).  This book can be read online at Google Books.
[9] A competitive bidding process involving sealed bids is referred to in an October 10, 1917 article in  Jeweler’s Circular Weekly.  A copy of that article can be seen in an earlier post titled “What to the Numbers 3500 and 1542 Tell Us? Part Three”.  How the sextant acquisition process worked at the turn of the 19th Century is described in the Department of Nautical Instruments section of the Report of the Superintendent of the United States Naval Observatory dated July 1, 1898: 
“The purchase of sextants by award of contract to the lowest bidder was so far modified to invite instrument makers to submit sextants made in accordance with careful specifications, the contract to be awarded at a stated price to the maker whose work showed the highest accuracy and perfection of work. Four firms submitted a sample of sextant of the two classes called for (a high-grade sextant at $100 and a surveying sextant at $90), with the exception of Warner & Swasey, who submitted only s high-grade sextant.  As a result of the competition, the contract for the high-grade sextant was awarded to Warner & Swasey, of Cleveland, Ohio, and for the surveying sextant to F.E. Brandis, Sons & Co of Brooklyn, N.Y.
[10] Page 8 of the U.S. Naval Observatory’s Annual Report for Fiscal Year 1918 reports on a ‘drive for glasses’ overseen by Assistant Navy Secretary Roosevelt.  Page 6 of the report explains that at the outset of the war, American manufacturers were unable to produce needed items at a sufficient pace, and that the production of optical glass at a sufficient rate to meet needs was a particular problem.
[11] A copy of the Four Minute Men memo can be viewed in the digital collection of the University of Colorado at Boulder:
[12] The numbers stated in the report would seem to be rounded to the nearest thousands; while the numbers are said to be for ‘glasses’, I suspect that they are for all types of equipment.  The serial number of the Captain Hooker sextant, RO 31518, is the highest of the five sextants discussed here, looks to be close to the end of the RO serial number series.