SIR G. GREENHILL ON ELECTROMAGNETIC INTEGRALS. 
37 
This was carried out by Mr. J. W. Hicks for comparison with Maxwell’s figure 
using the formulas given later in § 12. 
The same confocal co-ordinates on the Weir chart were employed by Colonel 
Hippisley in drawing fig. 3 and 4, and the lantern slides, showing the lines of 
uniplanar flow past an ellipse ; but here the co-ordinate ruling has been rubbed out. 
