Slide rules HOME page COLLECTION 10" RULES UNITED KINGDOM
Make PIC/Thornton, United Kingdom
Model 4639
Notes

1. This rule has a fairly standard arrangement of the scales, including 2 log-log scales on the stock and trig scales on the back of the slide. This may seem rather boring until one takes into account the fact that Thornton held a patent for differential trig and log-log scales. In the case of trig scales they enabled a wider range of values of both trig and inverse trig functions to be fitted into a smaller space. In the case of the log-log scales it enabled the range normally covered by LL0 and LL1 scales to be replaced by a single short scale. In both cases the drawback was the requirement for more slide movement. One can only assume that this rule was produced for users who were taught to use rules with more standard scales.

Front view
1046-pic3649-01.jpg (22585 bytes)
Detail - front left
1046-pic3649-02.jpg (14186 bytes)
Detail - back left
1046-pic3649-03.jpg (19052 bytes)
Manufacturing date c 1955
Length 10"
Material Plastic on wood.
Scales LL2, A [B, CI, D / S, L, T] B, LL3
Cursor Metal and glass
Documentation None.
Condition Good