Prof. Moseley on the Principle of Least Pressure, 95 



by Mr. Faraday*, and the exterior of a water reservoir by 

 Becquerelf. 



Most saline solutions, and the sulphuric and carbonic acids, 

 precipitate more or less of the lead from its solution in distilled 

 water, the neutral salts probably in the state of hydrate and 

 the acid salts and free acids in combination (22.). 



That carbonic acid dissolved in pure water does not act on 

 lead, or dissolve any measurable portion of its oxide, if at 

 least there be an excess of oxide present, but that it is capable 

 of dissolving a minute portion of the carbonate, though pro- 

 bably such a quantity as is equivalent to less than £th the 

 oxide which distilled water is capable of taking up (28 — 36.), 



The only spring water I examined which dissolved any 

 oxide of lead was free from carbonic acid (32.). 



That with reference to ceconomical purposes, it will proba- 

 bly be found that such spring waters as act most on lead, act 

 least on iron, and vice versa. 



That in the simple voltaic circle of lead and iron, when 

 both metals are bright, the lead is positive to iron, as Volta 

 originally placed it ; but that when the surface of the lead is 

 oxidized, it becomes negative to iron and copper. 

 12 Duke-street, Grosvenor-square, Philip YoRKE. 



May 2, 1834. 



XIV. On the Application of the Principle of Least Pressure to 

 the Theory of Resistances. By the Rev. H. Moseley, B.A. 9 

 Professor of Natural Philosophy and Astronomy in Ki?ig's 

 College, London.^ 



ET P t P 2 P 3 , &c, represent the different resistances of the 

 -*-' system ; u x p x y v a 2 p a y 2 , u s /3 3 y 3 , &c, their inclinations to 

 the axes ofxyz; x l y l z v x 2 y 2 z q9 x 3 y 3 z 3 , &c, the coordinates 

 of the points of resistance; u l = 0, u 2 = 0, u 3 = 0,&c, the re- 

 lations existing between the coordinates of the several points 

 of resistance, by reason of the connexion of the parts of the 

 "System ; M x M 2 M 3 , the sums of the resolved parts of the given 

 forces of the system (z. e. those which are not resistances) in 

 the directions of three rectangular axes; N x N 2 N 3 their mo- 

 ments about those axes. 



.*. .2P = minimum. 

 ZP cos a + M x = ") 



ZPcos/3+M 2 = V (1.) 



Z*P cos y + Mo = 0. J 



Journal of Science, vol.xvi. p. 163. f Ann. de Chimie, torn. liv. p. 146. 

 Communicated by the Author. 



