120 
Case I. Let \p=v(p(j). 
Then by (V) 
= Svpc - SpVo” 
and we get 
J’^'^padv — J'Sp'S/crdv = J'SYpff.vdS — JspffvdS VII. 
Case II. Let \p=(p(T, where ^ is a scalar. 
Then v+ = 
and J'S'^(J)<T.dvJ'S'S/(T.(l)dv = J^(j)Sa’vdS. VIII. 
Stokes’ Theorem can be made by similar treatment- to 
give varied forms, both more and less simple. 
PHYSICAL AND MATHEMATICAL SECTION. 
March 2nd, 1880. 
E. W. Binney, F.K.S., F.G.S., President of the Section, in 
the Chair. 
“Results of Observations of the double-period Variable 
Star R Sagittce,” by J oseph Baxendell, F.R. A.S. 
During the last two years I have observed six of the 
principal minima of this interesting variable, and as I had 
not made a redetermination of its elements since the end of 
18C1, or only two years after the discovery of its 
variability, I have reduced and projected all my observations 
made since that time and have obtained the dates of 26 
additional principal minima. The entire series from the 
