364 Proceedings of Royal Society of Edinburgh. [sess. 
the plates horizontal. The figures were lighted by a curved sheet 
of white cardboard placed above the camera, and illuminated by 
a gas jet or by burning magnesium ribbon. 
Curves of the same general nature as those drawn . by construc- 
tion or calculation were obtained for the cases shown in the table. 
The author is indebted to several of Professor Jamieson’s students 
for assistance in making the curves, and to Messrs Baird & Tatlock 
for the loan of the apparatus shown at the meeting. 
No. 2. Single Charge. 
No. 3. Unlike Charges. 
Robertson’s Dust Figures of Electrostatic Lines of Force. 
