1814.] made during the Year 1S13. 9 



mechanical force is measured by the mass multiplied into the square 

 of the velocity. The paper is written with great clearness and 

 precision ; but it would be doing it injustice to attempt to exhibit 

 an abridgment of it. We refer tliose who are interested in such 

 discussions to the '2d volume of the New Series of Manchester 

 Memoirs, published during the courte of 1813. 



For a similar reason we refer to the same book for Mr. Cough's 

 theorems elucidating the mechanical power called vis viva on the 

 continent. 



One of the most ingenious and useful mechanical inventions 

 lately proposed in this country is Dr. Wollaston's method of draw- 

 ing very fine wire. He takes a platinum wire, stretches it in the 

 centre of a mould, and fills the mould with silver. The silver is 

 then drawn cut into a fine wire. This wire is dipped into aqua- 

 fortis, which dissolves the silver, and leaves the central platinum 

 wire of extreme fineness. Dr. Wollaston's account of his process 

 is published in the Philosophical Transactions for 1813. 



VI. Electricity. 



Electricity is one of those branches of science which, after having 

 been for some time nearly stationary, has made an unexpectedly 

 rapid progress of late years; but the year 1813 has added little to 

 our previous electrical knowledge. 



M. Poisson has endeavoured to determine by calculation in what 

 manner electricity is distributed on the surface of conductors. He 

 begins by taking for granted the truth of the hypothesis that tliere 

 are two kinds of electrical fluids, the particles of each of which 

 mutually repel, while the particles of one fluid attract those of the 

 other. Conformably to this hypothesis, he has calculated the dis- 

 tribution of the fluid on two excited spherical bodies in contact. 

 The result of his calculations comes very near to the experiments 

 of Coulomb. He is employed in extending these interesting cal- 

 culations to new cases. 



Mr. Children's splendid galvanic battery, consisting of 20 pair 

 of copper and zinc plates, six feet in length, and two feet eight 

 inches in breadth, deserves to be noticed, bccatise it is the largest 

 of the kind that has hitherto been put in action. He lias not yet 

 laid the result of his experiments before the world. A short account 

 of them will be found in the Aiiuah of PInlo&opliy, vol, ii, p. Wj, 



Mr. Walker has observed that when an excited surface is brought 

 near the top of Bennct's electrometer, but net so near as to pro- 

 duce a spark, the gold leaves diverge in the same state of electricity 

 as the excited surface; but as soon as this surface is removed, the 

 gold leaves collajjse, and instantly diverge again in a contrary s'tate : 

 and these changes take place every time that the excited surface is 

 moved to and from the cap of the instrument. JSee Philosophical 

 Maga/iuc, vol. xli. p. 415. Mr. Singer has obser\ed that ihfs fact 

 had been lung known to electricians, and he gives an explanation 



