A Slight Price Change

I recently acquired a mid-1900’s copy of Ainsworth’s Brunton Pocket Transit owners manual. This is the small manual that was included with every pocket transit sold.

Brunton Pocket Transit 1957 - Front Cover

Click on the image to open the manual as a PDF

Included with this manual was a 1957 price list and the prices it shows makes for some fun comparisons to prices today

Brunton Pocket Transit 1957 - Price List

In 1957 an Ainsworth manufactured pocket transit would set you back $49.50. Wow! Compared to current pricing for the same item made today by the Brunton Company – $400 – that was quite a bargain.

Or was it? There’s no direct comparison between 1957 prices and 2016 prices. If we calculate for inflation using consumer price index numbers, $49.50 in 1957 dollars = $417.52 in 2015 dollars. So the pocket transit buyer in 1957 was actually paying about $17 more in inflation adjusted dollars for his compass.

Any way you calculate it a new pocket transit is a pricey piece of equipment. It wasn’t (and still isn’t) a purchase decision a young college student or newly graduated geologist made lightly, but it was a necessary and critical piece of his professional kit. That probably explains why there are so many well used but well cared for examples available today on auction sites like eBay.



The Brunton Cadet

This website has covered the Brunton pocket transit and its clones in-depth, but there’s one design that shares some of the classic pocket transit DNA that we haven’t looked at yet – the Brunton Cadet pocket transit.

Brunton Cadet

I’m not sure when the Cadet was introduced, but I’m guessing they hit the market in the late 1950’s or early 1960’s. The next question is, why? The cadet offers about 50% of the functionality of the classic pocket transit design (it lacks a needle dampening system, leveling bubbles, extended sighting vanes and an adjustable clinometer) and comes in at less than 1/4 the price of a base model Brunton pocket transit. My guess is that Ainsworth (the original manufacturer of both the Brunton pocket transit and the Cadet) was getting a lot of requests for a compass that had most of the features earth science students needed to get the job done, but at a much lower cost as compared to the classic pocket transit.

To answer the demand Ainsworth produced an all-plastic compass that is the same basic size and shape of the classic pocket transit but is greatly simplified. My example was produced sometime in the 1960’s, judging by the marking on the box. It offers a sighting mirror, clinometer and a compass ring set off in both degrees and quadrants (a neat idea that could have been migrated over to the standard pocket transit but, alas, never made it there). On my example the sighting mirror is a heavy piece of mirrored glass with a sighting line scored down the center and (I’m assuming) glued to the compass lid. The undampened needle has no obvious north markings on it save for a small hole punched in the needle to indicate the north end. The clinometer is a simple free swinging indicator affair set off in degrees of slope, but not percent.

Ainsworth claimed this is a ‘training’ compass, intended to teach students how to use the full featured pocket transit. Printing on the side of the box even states that the Cadet affords “… all the applications of the Brunton Pocket Transit, Basic Mapping Procedures, Plotting, Dip & Strike, Clinometer, Alidade, Prismatic Compass”Boy that’s a load of bull! Without bubble levels it is impossible to do accurate strike and dip measurements on rock formations, so the Cadet’s usefulness for geology field work is limited. Without the sighting vanes it is impossible to use it as an alidade. With an undampened needle it’s extremely difficult to use it as a plotting tool or to accurately set a bearing. And it’s not a prismatic compass, it’s a mirror compass. Clearly the advertising guys at Ainsworth never took these things to the field before writing the copy. What the Cadet does remind me of is an old forester’s compass, but with a few added features. Perhaps it was designed to steal market share from the Silva Ranger compass, which was gaining in popularity in the US in the post-war period among foresters and others who needed to do rough field work with a map and compass.

Brunton Comparison 2Ainsworth Brunton pocket transit and the Ainsworth Cadet. Both were manufactured around the same time period

But the Cadet design (or price) must have resonated with many college and university earth science departments because I remember seeing them in the pile of pocket transits available in the geology department when I was attending school. I never used one – as a poor geology student I relied on my Silva Ranger for map and compass work and if I needed to do strike and dip measurements I just borrowed someone’s pocket transit.

Brunton Cadet Manual Front

Brunton Cadet owners manual (click to open)

Which leads, I guess, to the point of this post. The Brunton Cadet is interesting if you like to study the lineage of pocket transits, but it really doesn’t work all that well in today’s world. If you need a pocket transit just suck it up and buy a full featured model. The Cadet is still produced by Brunton and right now is sells for a little over $40 on Amazon. It’s a big step up in price to the cheapest full featured pocket transit, the Brunton ComPro (at just under $250 on Amazon), but the ComPro is a professional instrument and well worth the investment. If you just need a sighting compass there’s any number of mirrored sighting compasses available close to the Cadet’s price point that do a much better job. My personal recommendation is the Suunto MC-2.

We’ll just call the Cadet an evolutionary dead end on the pocket transit tree of genetic diversity. An interesting item for study, but one pushed out of the ecosystem by more evolved competitors.


More Money Than Sense?

Last night on eBay someone plunked down $1,200.00 (plus $25 shipping) to purchase a used Brunton pocket transit. Silly impulse purchase? A case of SUI (Surfing Under the Influence)? Or does the buyer know something I don’t?


This auction opened and closed on the same day. The opening bid price (set by the seller) was $700, with a buy-it-now price set at $1,200. I thought $700 was somewhat high, but clearly someone else thought $1,200 was just right

You see, this particular Brunton appears to sport the serial number 232 (although it’s hard to make out in the lousy photos the seller provided). If the serial number is valid this puts it somewhere in the first or second year of production – around 1895. This is by far the earliest production Brunton I’ve ever seen for sale.


Given what information could be gleaned from the poor photos the seller provided, this transit looks right for an early model – hand engraving on the lid (with no sine tables), small view hole in the lid, no lid mounted peep sight, no tripod bracket slots and a single tube level on the clinometer

I sincerely hope the buyer is happy with his/her purchase. Who knows, perhaps it’s destined for a museum collection (which might explain why it sold so fast at the buy-it-now price). If the buyer happens to read this blog I’d love to hear more about your decision to purchase this pocket transit and perhaps provide a few detailed photos of this remarkable example to share with the readership.

I’ve added this Brunton to the Pocket Transit Serial Number Project spreadsheet so we have a record of its existence and sale. To date it is the second oldest Brunton on the list. I’d love to know more about its history – who owned it, where it was purchased, where it was used. These fine old instruments usually have a great story to tell.

– Brian


Pocket Transits

One of the most popular series of posts I did on my old blog site were related to the Brunton pocket transit. This device – a large pocket compass with a built in level and clinometer – could be found in the pocket or on the belt of geologists, map makers, mining engineers, hydrologists, and foresters across North America and around the world. It is a tool that has no equal for rough field survey work, and the fact that it survives essentially unchanged from when it was first patented in 1894 is a testament to the ingenuity of its inventor David Brunton.

When I first wrote about pocket transits back in 2010 there was a wonderful web resource for collectors and enthusiasts titled Brunton Pocket Transits that was compiled and hosted by William J. Hudson.  Mr. Hudson did an outstanding job of researching the history of David Brunton and the development of his pocket transit.  Mr. Hudson also started a serial number project, cataloging the serial number ranges and production dates from different manufacturers to allow pocket transit owners to better establish the production date for their instruments.

Unfortunately in 2012 Mr. Hudson’s site went off-line and many feared this resource was lost forever. Well, with the world wide web nothing is really lost forever. I was recently contacted by one reader who was able to find a full archive of the site on the web archiving site Wayback Machine. I have since been able to contact Mr. Hudson and he’s given gracious permission to use any and all information that used to be hosted on his site.

I was able to convert most of the web pages from the Brunton Pocket Transits web archive to PDF format and I’ve transcribed Mr. Hudson’s serial number data into spreadsheet format for easier updating and sharing.

All of this information, including much of the text from my original blog posting, is now available from the Brunton Pocket Transit link under the Resources link at the top of the page.

If you have any information you’d like to pass along, including information about specific pocket transits you’d like to have included in the serial number archive feel free to contact me using the contact information at the About link at the top of the page.

– Brian

Brunton Pocket Transit Brochure

Let’s continue our conversation about the Brunton Pocket Transit.  In the past we’ve talked about how useful the pocket transit is, some of the different models available, and I’ve touched on some Brunton-related web resources.

So today let’s take a look at a small brochure that William Ainsworth & Sons (the manufacturers of Brunton pocket transits for most of the 20th Century) used to make available to pocket transit customers.  This particular little booklet was published in 1929, but the illustrations look somewhat older than the late 20’s, so I’m guessing this is a reprint of an earlier brochure.  The brochure is small – just a bit larger than a 3″ x 5″ index card and it’s only 21 pages.

It’s an extremely useful little book, because it covers in some detail the different ways you can use the pocket transit, whether it’s shooting azimuths, reading horizontal or vertical angles, tracing a mineral vein or using the instrument as a clinometer or a plumb.

There’s even instruction on how to use the pocket transit in conjunction with the ‘Wilson Magnetometer Attachment’, a real Rube Goldberg device that is intended to be mounted to a plane table to measure large anomalies in magnetic intensity found in mineral bearing rock formations.  I’ve never seen a Wilson Magnetometer in person, but I’m keeping my eye out for one!

There’s a lot of useful info stuffed into these 21 pages and I thought it important to make the booklet available to the collector community.  You can click here to download the pamphlet as a PDF file (about 1.6 mb).  You can also access the individual pages as images by clicking here to access my Picasa site.

So you Brunton fans out there, enjoy!

Update!  Just today I was doing a Google search on a topic related to Brunton pocket transits and I ran across an interesting booklet titled “Enterprise & Innovation In The Pikes Peak Region” published in 2011 by the Pikes Peak Library District.  In the booklet is a very informative article about David W. Brunton, the inventor of the Brunton Pocket Transit.  There’s a very good discussion about the development of the pocket transit.


William J. Hudson’s Pocket Transit History Site

Several times in this blog I’ve referenced an excellent pocket transit history site established by a gentleman by the name of William J. Hudson.  His site was the resource for historical information on the development of the pocket transit, its many variations and changes down through the years.  I considered it the best resource on pocket transits available anywhere on the web.

Unfortunately it looks like Mr. Hudson’s site went off-line well over a year ago.  I first noticed it about six months ago while doing some research on a pocket transit I had just added to my collection.  Over the last few months I’ve been contacted several times either directly or through this blog about Mr. Hudson’s site, asking if I knew when it might be available again.  Since I don’t know Mr. Hudson and I’ve never communicated with him I had no way of contacting him to see when or even if he intended to reestablish his website.  It seemed a great resource for those interested in pocket transits was gone from the web forever.

Well, things don’t really disappear from the web.  They just get archived.  I’m happy to report that I’ve stumbled upon an archive of the main page of Mr. Hudson’s site hidden away in a dark corner of the internet.  Unfortunately none of the linked pages such as his serial number breakdown page were archived, so that resource appears lost.  But the main page is still chock full of useful information about the pocket transit’s history, development and features.

I’ve linked to the internet archive for this page from the image below.  When you open the page you’ll have the option to download the page and graphics as a zip file.

Click here to access the site archive

I’m glad to have access again to at least a portion of this great resource.  Mr. Hudson, if you read this, can we have your site back please?  Hundreds a couple of diehard pocket transit collectors really miss the information your site provided!


The Pocket Transit

In Which Way North? (Part I) we discussed the history of the magnetic compass and talked a bit about magnetic declination.  Now let’s start looking at some specific compass designs and discuss why they were important.

To start we’ll look at a compass design that is uniquely American and was born of the late 19th Century explosion of mining and mineral exploration in the US.  This compass was originally conceived to fit a very specific need, but it was so well designed and executed that it found use in a wide variety of applications and industries.  It continues to be produced today, over 100 years since its introduction and little changed from its original design.

The Brunton Pocket Transit was patented in 1894 by David Brunton, a Colorado mining engineer.  Brunton was frustrated by the number of survey instruments a mining engineer and geologist had to carry around with him (and I say ‘him’ because mining engineering and field geology was an exclusively male profession well into the 20th Century).  In the late 1800s it was not unusual for engineers and geologists doing basic exploratory mineral mapping to lug around full sized survey transits, surveying compasses, tripods, clinometers, and plane tables. These instruments offered a high level of accuracy that simply wasn’t needed for exploratory surveys.  As an engineer himself Brunton realized that what was needed a portable device that allowed field survey personnel to do fast and accurate exploratory quality surveys without being burdened down by equipment that was heavy, expensive and difficult to set up and use.  These men were in the business of discovering, verifying and mapping mineral deposits that covered vast areas.  Huge sums of money were at stake as mining and mineral companies scrambled to secure valuable leases on the stuff that was fueling America’s exploding industrial economy – timber, gold, silver, coal, iron ore, chromium, nickel, bauxite, petroleum and dozens of other minerals that were key to America’s growth.  Field engineers and geologists needed to move fast, do rough mapping and get that information back to the office for the development of lease maps and boundary descriptions.  They didn’t need to be burdened with heavy, sensitive and fragile survey gear if that level of accuracy wasn’t required.  David Brunton recognized the problem and set to work developing a solution.

What Brunton came up with as a pocket-sized device that incorporated an accurate magnetic compass with a sighting vane, a clinometer, a level and a large mirror with a sight line.  Housed in a machined aluminum case (still an expensive material in the late 1800s), it was rugged, reliable and useful.

Brunton named his instrument the ‘Pocket Transit’, a lofty title for a fairly rudimentary mapping device.  But the name served its intended purpose; in the mind of the engineer and geologist it set the device apart from the common handheld compass.  Here was a professional instrument that offered a level of accuracy and functionality not found elsewhere.

Brunton’s 1894 model Pocket Transit

Brunton had more than marketing on his side.  The Pocket Transit actually delivered where it mattered – in the field and in the hands of engineers and geologists across North America.  It delivered all the functionality and accuracy needed to get the job done.  It ended up being the perfect device for the job at hand.

Demand for Brunton’s device increased steadily and improvements were introduced.  An additional bubble level and a cover mounted peep sight were added in 1912.  In the same year Brunton introduced modifications to the case that allowed mounting the instrument on a non-magnetic tripod or jacobs staff.  (It’s interesting that in his 1894 patent application Brunton derided other compass designs that needed to be tripod mounted, but in the 1912 patent application he discusses tripod mounting like it’s the greatest idea since sliced bread.)  Somewhere between 1894 and 1912 the Pocket Transit acquired the ability to pre-set magnetic declination by use of an adjustment screw on the side of the case.  By 1926 Brunton’s design had fully matured with the addition of a bullseye level for improved leveling and the addition a percent grade scale to the clinometer.  From this point forward it was minor improvements in materials, manufacturing techniques and the added availability of different compass ring layouts (degrees, quadrants, mils, etc.)

A 1926 patent model of the Brunton  Pocket Transit.
Note the round level and the percent grade indices
at the bottom of the clinometer scale.  This is the basic
design still in production today.
One of the reasons Brunton’s pocket transit was
so damned useful is that he made it a complete package.
Early in the production of the pocket transit Brunton started
engraving sine and tangent tables on the lid.  Using these
tables in conjunction with the clinometer an engineer could
quickly and accurately determine heights of objects like trees
or cliff faces.  To this day Brunton includes the sine and
tangent tables on the lids of all pocket transits.
So damned useful!
From the beginning David Brunton licensed the Colorado instrument maker William Ainsworth & Sons to produce the pocket transit.  After Brunton’s death in 1927 Ainsworth purchased the manufacturing rights to Brunton’s designs and continued manufacturing and improving the Pocket Transit through the late 1960s.  In 1972 the production rights and the Brunton name were purchased by the Brunton Company of Riverton, Wyoming.  The Brunton Company continues to manufacture this basic design.

The Brunton design was so well thought out that engineers and geologists quickly developed field techniques keyed to the Pocket Transit’s unique layout and construction.  The best example is the determination of the strike and dip of rock formations.  Most sedimentary and metamorphic rock formations are not horizontal.  They were all deposited in horizontal layers but over geological time (i.e., millions of years) those horizontal layers have been warped and deformed by pressure and other geological forces.  One of the keys to understanding these forces is mapping the strike (the horizontal angle of deformity) and dip (the vertical angle of deformity) of individual rock layers.  Before the Brunton Pocket Transit the measurement of strike and dip was a clumsy process involving two separate devices – a field compass (often a fairly large and somewhat fragile device) and a clinometer.  With the Brunton the process is quick and simple – open the instrument and lay it horizontally against the rock formation.  Keeping the edge of the instrument in contact with the rock face rotate it up and down slightly until the circular level is centered.  Note the magnetic azimuth as indicated by the compass needle.  That is your strike.  Score a line on the rock face horizontal to the pocket transit using a piece of chalk or small piece of rock and remove the pocket transit.  Make another score mark that is perpendicular to the horizontal mark you just made (your mark should look like a ‘T’).  Place the Pocket Transit along this perpendicular mark and measure the angle of slope using the built in clinometer.  This is your dip.  It takes longer to describe than it does to do it in the field.  This is the standard measurement technique for strike and dip, and every college and university geology department in North America teaches it as part of their field geology curriculum.

From the University of Calgary website.  Measuring the strike
of a rock formation using a Brunton Pocket Transit.
From the University of Calgary website.  Measuring the dip of
a rock formation using the Brunton Pocket Transit.
My introduction to the Brunton Pocket Transit came in the mid-1970s while studying geology in college.  We learned strike and dip measurement techniques early on in the field methods class, and later during our summer field geology course we ranged across the southwestern United States, making thousands of strike and dip measurements in an effort to understand the geologic processes that formed the unique landscape of that region.  I saw the Pocket Transit as a useful but fairly limited device, suited only to the field geologist.  Years later while attending a course at the Defense Mapping School at Fort Belvior, Virginia, our class got an intensive block of instruction on the use of the Pocket Transit not just for strike and dip measurement but for height determination, precise azimuth determination, basic plane table survey work and rough site layout.  I finally saw the full potential of the Pocket Transit and purchased my first one soon after.  That Pocket Transit has seen service in Kuwait, Honduras, Panama, Germany, Bosnia, Korea and across the US.  It has been a constant companion on hundreds of field surveys, assisting with tasks like mapping out refugee camps on the Empire Range area of the Panama Canal Zone, measuring road grades along the Pan-American Highway in Honduras and fixing North Korean observation point locations along the Korean DMZ.

The Brunton Pocket Transit doesn’t measure horizontal angles as well as a conventional transit, it doesn’t measure vertical angles angles as well as a theodolite, sextant or even an Abney hand level.  If you need to shoot azimuths using handheld techniques the Army lensatic compass is a better tool.  However, the Pocket Transit does all of these tasks well enough, and puts everything needed into a compact, easy to carry package that really does fit into your pocket.  (In his patent application David Brunton noted that the instrument fits nicely into a vest pocket – therefore the name pocket transit).

Let’s have a look at some Brunton Pocket Transit variations (click on the pictures for an enlarged view):

This is a modern incarnation of the Pocket Transit – a glass filled composite
body version.  This particular Pocket Transit is almost 20 years old
and has been used around the world, and it still looks new.
This is a particularly nice WWII era Pocket Transit manufactured in 1943.
This model is graduated in mils (6400 mils in a circle).  Designated the
M-2 Compass, it was designed for use by artillery troops who need a more
discreet subdivision of the circle for accurate artillery gun laying and spotting.
A variation of this model is still used by the US Army and USMC today.
An early induction dampened model graduated in degrees
A nice post-war model graduated in quadrants instead of degrees.
Most early Pocket Transits were sold with the quadrant setup rather than
degrees.  The use of quadrants was the accepted method of noting direction
within the engineering and geology community up through the 1970s.  Brunton
still sells a modern version of this layout, but it really is useless for general
navigation purposes.  If you want to do land navigation with a Pocket
Transit get the model laid out in degrees!

As you can tell, I think the Brunton Pocket Transit is a nifty little tool.  But it is not a novelty, not something to be put on a shelf to be admired.  The Pocket Transit is designed and built to be used.  It represents American ingenuity at its best.  From 1894 on the Pocket Transit ended up being used in all corners of the United States, doing useful, often rough duty helping to map American and her natural resources.  Rugged, reliable, useful.  American to the core!


In writing this blog post I relied heavily on several sources that I feel need to be acknowledged.

First is William Hudson’s excellent website About Brunton Pocket Transits.  Mr. Hudson’s site is the most complete compilation of information about Pocket Transits on the web, and should be the starting point for anyone interested in finding out more about these great little devices.  Thanks you Mr. Hudson.

Next is Dr. Peter H. von Bitter’s article The Brunton Pocket Transit, A One Hundred Year Old North American Invention.  Originally written in 1995 for the journal of the History of the Earth Sciences Society to celebrate the 100 year anniversary of the invention of the Brunton Pocket Transit, von Bitter’s article forms an excellent short history of the man David Brunton and his famous invention.  Thank you Dr. von Bitter.

Although not source, there is an scanned copy of a 1913 Ainsworth bulletin available on the the Surveying Antiques website.  This bulletin describes the various ways to hold and use the Pocket Transit and is an interesting overview of the instrument and its uses.