1. It is interesting to compare this rule with the Simplon Bilateral from the same maker which tackles similar problems in very different ways.
2. One feature not often found is the bevelled slide, as opposed to the more normal tongued and grooved slide.
3. The rule has the trigonometric scales on the reverse of the slide, however as with the Simplon Bilateral, they cannot be directly transferred to the face of the rule. To allow for the fact the sine scale becomes cramped for angles above 70º there is a table of values of sine from 71º to 90º on the slide.
To allow for calculating the tan of angles less than 6º there is a table of values of tan from 0º to 5º 40' on the slide.
4. On the reverse of the stock there is also a scale of logarithms and a D scale. The cursor is not however reversible.
Front view
Back view
Detail - front view
Detail - back view
Showing D and Log scales
Detail - slide
Showing table of sines
Detail - slide
Showing table of tangents
Detail - showing bevelled slide
On the rule these scales are named LU, A [B, unnamed, C / A, Sine, Tan, D] D, LL \ Log, D
c : 1.13: C,D
c': 3.57: C,D
M: 31.8: A,B