Phil. Mag. Ser. 6, Vol. 9, PL VII. 



Fig. 1. 



£ 3 4 5 6 7 8 9 lO II \l 13 10, 



d/staa/ce ih cms. betwfb/v movable s/oes. 

 Fig. 2. 



15 16 17 18 19 20 2\ 22 



5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 2' rt 



D/sta/vce //* cm between movable sides. 



