Feb. 14, 1876. 
THE PRESIDENT (PROFESSOR CLERK MAXWELL) in the Chair. 
The following communication was made to the Society: 
On the effect of the constant current on the Heart. 
By Mr Fosrer and Mr Dew Smiru. 
Feb. 28, 1876. 
THE VICE-PRESIDENT (PROFESSOR BABINGTON) in the Chair. 
The following communication was made to the Society : 
On Bow’s method of drawing diagrams in graphical 
statics, with illustrations from Peaucellier’s linkage. 
By J. Cuurx Maxweit, M.A., Professor of Hu- 
perimental Physics. 
The use of Diagrams is a particular instance of that method 
of symbols which is so powerful an aid in the advancement of 
science. 
A diagram differs from a picture in this respect, that in a 
diagram no attempt is made to represent those features of the 
actual material system which are not, the special objects of our 
study. 
Thus when we are studying the internal equilibrium of a 
particular piece of a structure or a machine, we require to know 
its shape and dimensions, and the specification of these may 
often be made easier by means of a drawing of the piece. 
32—2 
