Modern instruments and methods of calculation : a handbook of the Napier Tercentenary Exhibition (1914)
Horsburg, E. M. (Ellice Martin), Napier Tercentenary Exhibition (1914 : Edinburgh, Scotalnd) · London : G. Bell · leaf 221
attempts by Wetli 1 in 1849 to improve planimeters resulted inthe substitution of a circular disc for the cone, as we have already mentionedhad been done by Gonella, and it is clear that the above theory obviously 7T applies, for the cone may be degenerated into a circular disc by making a =-… … Fig. 2. In the 1851 Exhibition in London, various types of planimeters wereexhibited, among which was one by Sang.2 The combination of rolling andslipping of the integrating wheel in all the above forms of planimeters is notentirely satisfactory, and Maxwell,3 being struck with this imperfection…
