Brunton Compass

Brunton Pocket Transit, folded for carrying.

This is a Brunton Pocket Transit.  Probably most people who know of them just think of them as the Brunton Compass.  It's an old, old design, having been first made in 1894, although the patent date on the compass references 1896.  I'd be curious to know when  they really started to be common, if we can consider a specialized instrument like this as ever having been common.

I ran across my Brunton compass recently as, for some reason, I'd taken it out of the carrier this fall in order to use it for something.  At this point, I frankly don't know what that something was, as I very rarely use it anymore.  I have a nice Garmin GPS with the topographic map software loaded into it, and I use that now, even though its a model that's now discontinued, and the last software up data makes it a little slow

Brunton Pocket Transit, opened for use in the geologists fashion.

I sure remember getting the compass, however.  It was in 1986, during my last year at the University of Wyoming, when I was a geology student. We had to buy them for our summer field course, which took us all over Albany and Carbon counties, mapping, and all the way down to New Mexico, where we did field work, as well.  At that time, having a compass of this type was an absolute necessity, and they saw 100% employment by geologists who did field work.  I'm told that at one time, graduates of the mining engineering school at the Colorado School of Mines could be identified by the short brim Stetsons they all acquired upon doing their field work (back in the sensible headgear days).  If so, graduates of any geology program anywhere could be identified by the fact that they all owned Brunton compasses.

Brunton compass opened up with mirror facing to catch the sight, in the fashion used by geologists in the field.

The reason for this wasn't fashion, it was necessity.  The compass is a precision instrument, and the official name of "transit" is accurate.  A transit is a surveying instrument, and so is a Brunton compass.  Extremely precise, the location of about anything can be accurately determined by triangulation or even just flat out using it in concert with a drawing compass (the plastic device) and a topographic map.  But we made topographic and geologic maps with them, which requires not only the compass, but more work.

Compass opened, showing the interior device for measuring angles, for determining elevation.  This one is not set, as the level clearly shows.

The reason that the compass can do this is that it not only features the typical magnetic compass feature, but it also has the ability to sight elevations with the use of an internal scale.  And when set on a Jacob's staff, a pole of a known size, distance on the ground may be measured over any sort of terrain while using that feature, with the compass attached to it, while the mapper walks over the ground.  A marvelous instrument.

My first exposure to this instrument didn't come in a geology class, however.  It came at Ft. Sill Oklahoma.  The Brunton Pocket Transit, to soldiers, is known as the artillery compass, and that's where I first learned how to use it, in basic training.

Compass set to site in the Army fashion.

I was actually surprised to learn, while a geology student, that my old friend the Brunton Compass, was used as a geologist's tool.  I just thought it was a marvelously precise Army compass.  Adapting to geology use was, therefore, very easy, even though the Army uses the sights differently.

Compass set to sight in the Army fashion.

Artillerymen used the compass as it is so much more precise than the conventional infantry compass, and artillery needs to be spotted accurately.  Even so, we never used it to the same degree of precision that geologists did.

Combined geology use and artillery use made me glad to have one, even when it turned out that I was never going to be a field geologist, that occupation having entered one of its cyclical slumps at that point in time at which I graduated from the University of Wyoming.  It's just been a field companion since then, which I used for many years when out in the sticks.

But not so much lately. As noted, I've gone to the GPS, although I was a late adapter of that technology.  Indeed, I hadn't looked at the compass for quite some time.

In looking at it, and then determining to post, I thought that it was probably a thing of the past now, but I see that this is one of those many things to which Yeoman's Second Law of History apply, they're still being made today. And they're still pretty pricey, although all in all I actually think they aren't as expensive in real terms now as they used to be.  Indeed, my recollection on this may be inaccurate, but I think the Classic model with the Aluminum body is now cheaper than the plastic cased variant shown in these photos.  It pleases me, frankly, so see that such a useful item is still in use.

I don't know if they're still in Army use or not, but I did learn the following, thanks to Gordon Rottman who sent me the text from his book on World War Two equipment:

M1 and M2 compasses with M19 carrying case This sophisticated compass was based on the William Ainsworth & Sons-made D. W. Brunton’s Pocket Transit dating back to 1894, but adopted by the Army in 1918. The M1 designation was assigned in the 1930s. The “artillery compass” combined a highly accurate surveyor’s compass with a clinometer (for measuring vertical angles and slopes), tubular horizontal level, and circular bubble plumb (vertical level). The circular level was for leveling the instrument before the azimuth values were read and the tubular level for measuring horizontal angles. There was an angle-of-site mechanism and an azimuth scale adjuster assembly making this a complex instrument requiring specialized training. It was used by artillery forward observers. It had a dustproof and moisture proof, dark OD-painted brass case (smooth or crinkled finish), squarish in shape with rounded corners, 2-3/4 x 3in and 1-1/8in thick; 5-7/8in long when  opened exclusive of the sights. A mirror was fitted inside the lid with a black sighting wire. The mirror also proved useful for shaving. There was a black folding front sight on the lid’s top edge. On the rear was a black hinged rear sight holder with a folding sight on top. The compass card was black with white markings. The M1 compass was graduated in degrees only and was phased out before the war by the M2 graduated in mils. M1s may have seen limited use. The mil scales was graduated at 20-mil intervals with 10-mil intermediate tick marks divided into 1-mil ticks. The angle of sight scale was graduated in mils in the same manner, 1200-0-1200 mils. On the compass card, north was indicated by a star and the other cardinal directions by W, S, and E. The radium-painted white end of the needle indicated north. The light brown leather M19 case had a rigid rounded pocket with a snap-secured lid and a trousers belt loop on the back. The rigid dark OD  plastic case (10543560) is post-WWII. Today it is known as the “M2 unmounted magnetic compass.” 0.5-b.

Pretty impressive.  Showing that the test of a tool is its usefulness, not its age.