The Scottish Mountain Heritage Collection
1001.2012.1
Mils protractors
29/08/2012
Hermione Cooper
29/08/2012
Two semi circular clear plastic Mils protractors.
One 6" and one 9"
plastic
23(l) x 14(w) cms and 15(l) x 9.5(w) cms
2
"PROTRACTOR 9IN. MILS MK 1 OS BRL 71619"
"PROTRACTOR R.A. 9IN. MILS/METRES MK1 A.B. OS. 80875 1979"
clear
PROTRACTOR (noun) an instrument for measuring, or drawing angles on paper, usually a flat semi circular transparent plastic sheet graduated in degrees.
Protractors can be, and still are, used in various other areas such as engineering, technical drawing, surveying and plotting charts, so we thought it best to point out that these ones are/were for map reading.
When Swedish orienteer and instrument maker Gunnar Tillander combined a protractor with a simple compass back in 1928 to create what we now call a baseplate compass, he literally consigned the protractor to the history books as far as outdoor folk were concerned. The trade name for Tillander's compass became Silva, a name that is now synonomous with all baseplate compasses, even if they are not made by Silva.
Protractors can still be used of course, and still are, in navigation at sea when plotting a course, and artillerymen still resort to them when their electronics fail, but in the great outdoors the silva type compass reigns supreme.
Way back in the depths of time, the Babylonians charted the sun movement across the sky concluding that there were 360 cycles or circles in a year. Whilst this has now been adjusted by a day or two, 360 became the basis of a circle and was the obvious choice for early compass makers who needed a certain amount of degrees in a circle and that's pretty much how it stayed up until the 1960's.
In the 1960's the American, and subsequently the British Army, adopted the Mils system of dividing up a compass circle and by a rather complicated system of mathematics they arrived at the figure of 6400 for a full circle - so North is seen at 6400 and South at 3200 etc. Even more confusingly, the French came up with a system of 'grads' of which there were 400 - they didn't like it very much but the Swedish did - and adopted it!
Anyway, the two protractors we have here in the collection are of the Mils variety and once belonged to Mick Tighe.
P.S. if you are interested in the origins of a MIL, check out circles, pi-radians and their wee mates mil-radians.
Donated by Mick Tighe
29/08/2012
29/08/2012
Spectrum : UK Museum documentation standard, V.3.1 2007
29/08/2012