52 Proceedings of the Royal Society of Victoria. 



Xj and X.J for otliei' windings, and for windows of other shapes 

 by inteipolation. 



[Note that tlie central section always belongs to coil 2 of i 

 sections, i odd.] 



50. There is also magnetic leakage due to the lines in the 

 copper conductors, and in the spaces between them, which is of 

 considerable importance in the case of large, low-pressure trans- 

 formers. 



It is well known that the inductance per unit length of a wire, 

 due to the lines in itself is 1/2, and due to the lines between its 

 surface of radius r and a concentric cylinder of radius r' is 

 21og^-';V. In the case of insulated wire wound in a coil it will be 

 very near the truth to take for r' the radius of the circle equal in 

 area to the total area allowed each wire in the winding, so that 

 if g be the space-factor 



and the inductance of the wire per unit length will be 

 i + log-- 



Hence, if / be the mean length of a turn of either coil, their 

 inductances arising from this cause are 



L"V=«,/||+log^^^} 



