Aus der Patentschrift GB191413073
"Proportional calculators.-In apparatus having two main graduated stationary arms A secured at an angle, preferably a right-angle, the adjustable members consist of a third side or hypoteneuse member B, pivoted to one end A<5> of one of the graduated members, and of two sliders C, E adapted for adjustment upon the graduated stationary arms and provided with clamping-screws C<1>, E<1>. A rectangular strut member D, having limbs D<4>, D<5> passing freely through apertures in the sliders, constitutes a means for correlating the positions of the sliders with the angle of the hypoteneuse member, for which purpose the apex D<1> of the strut may be clamped in a lengthways slot of the member B. One of the sliders may be dispensed with, and the corresponding reading taken at the edge of the limb of the strut member. ..."
Modell nach der Patentschrift
Multiplikation und Division mithilfe des Strahlensatzes.