Col. Yorke on the Solubility of the Oxide of Lead. 17 



time t, in consequence of the velocity of propagation combined 

 with the velocity of the aether at a, and suppose thatyis 

 brought to d in consequence of the difference of velocity of 

 the aether at a and b. It is easy to show that df is equal and 

 parallel io c c, so that, according to this construction, the nor- 

 mal to the wave ought to be displaced by the motion of the 

 aether through the angle /6d from /"ft to db, which is just the 

 contrary direction to that given by Prof. Challis's construc- 

 tion. 



Prof. Challis seems to think that the undulatory theory of 

 light cannot be maintained unless it can be shown that the 

 law of aberration ought to be the actual law, whatever may 

 be the motion of the aether. But it is surely sufficient to show 

 that a conceivable kind of motion exists which would lead to 

 the observed law of aberration, provided we have no reason 

 for regarding that sort of motion as improbable. Now even 

 were I to allow that udx + vdy+ wdz cannot, in the case of 

 ordinary fluids, be an exact differential unless the motion is 

 rectilinear, that would not be a fatal objection. For the equa- 

 tions of motion of fluids commonly employed are formed on 

 the hypothesis that the mutual action of two elements of the 

 fluid is normal to the surface which separates them, whereas 

 one of the most remarkable properties of the aether with which 

 we are acquainted, is the great tangential force which it is ca- 

 pable of exerting, in consequence of which the transversal 

 vibrations which constitute light are propagated with such an 

 immense velocity. 



VI. On the Solubility of Oxide of Lead in Pure Water. 

 By Lieut.-Col. Philip Yorke*. 



T N the Philosophical Magazine for August 1834, I published 

 ■*■ a paper on the action of water and air on lead. Some of 

 the principal results contained in it were confirmed by Bons- 

 dorff in two papers ; he found that 7000 parts of pure water 

 free from access of carbonic acid dissolved one of oxide of 

 lead ; my experiments gave y^^th to ^^th. Since that time 

 two papers have appeared on the same subject, one by Dr. 

 Christisonf, and one by Mr. R. Phillips, Jun.J The last- 

 named chemist considers that the oxide of lead is not dis- 

 solved, but merely mechanically suspended in the water, be- 

 cause the liquid is deprived of the lead by passing it through 



* Communicated by the Chemical Society ; having been read May 17, 

 1845. 



t Transactions of the Royal Society of Edinburgh. 



X Chemical Gazette for Jan. 1, 1845. 

 Phil. Mag. S. 3. Vol. 28. No. 184.. Jan. 184-6. C 



