Prof. Thomson's Geometrical PropositioJi. 



41 



I employ two copper cylinders of the same height as that in 

 the larger battery, and two wooden ones standing between the 

 copper cylinders, a cylinder of zinc being placed between the 

 former, by which means both surfaces of the zinc are opposed 

 to surfaces of copper, and greatly increased power is obtained 

 in the same space. This mode of arrangement, however, being 

 somewhat more complicated and expensive, may not be ap- 

 proved of so much for general use, nor be employed except in 

 cases where very powerful quantity effects are required. 



In conclusion, I would add that ];th of the quantity of the 

 solutions used in other batteries of the same extent of surface 

 will suffice for those described, without any loss of power. 



In the next Number of the Philosophical Magazine, I hope 

 to be able to make some observations upon the proper pro- 

 portions of zinc and copper in voltaic combinations, and in 

 reference to the investigations of Mr. Binks upon the same 

 subject, which have much interested me. 



Cheltenham, June 2, 1839. 



VIII. A Geometrical Proposition. By jAMEsTHOMsoN,ZyZy.Z)., 



Professor of Mathematics in the Unii)ersity of Glasgow. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



I SHALL feel obliged by your inserting in your Magazine 

 the following proposition, which I believe to be new, and 

 which is certainly curious. 

 Glasgow College, June 10, 183!). JamES ThoMSON. 



Let ABC be a plane triangle, and through any point P 

 in its plane, let A D, B E, C F, be drawn, cutting the sides, 



K 



or the sides produced, in D, E, F : through D, E, F describe 

 a circle cutting the sides, or the sides produced, in D', E', F': 

 join A D', B E', C F' : these lines all pass through a common 

 point P'. 



