244. 
(2) On a machine for illustrating the “ Parallelogram 
of forces.” By J.C. W. Ets, M.A. 
It consists of three graduated circular lamine. To the rim 
of each at the point 0° is fixed a weight w. Round the axle of 
each is wound a thread. The laminz are supported vertically 
on moveable stands. These stands slide along the three spokes 
of a horizontal wheel and may be fixed at any distance from its 
centre. These spokes again are capable of moving indepen- 
dently around their common vertical axis so as to take up any 
angular position with regard to each other. P is an index 
fixed vertically above the centre of each lamina. It can be 
easily proved experimentally that the tension of the thread will 
be proportional to the sine of the angle between W and P. 
The three threads are all joined to a little rmg & so as to rest 
horizontally on a horizontal circular graduated lamina attached 
