Integration of Differential Equation of the Second Order, 219 



Pacific Ocean on the coast of California, considered by Mr. 

 Veatch to be due to volcanic action #. Ramraelsberg has de- 

 tected boracic acid in sea- water and in sea- weed ; but where, I 

 cannot say, as I have not access to his paper. 



To the minerals found in gypsum, Dr. Dawson says, "I may add 

 peroxide of iron and bituminous and carbonaceous matters." As 

 regards the former, I should certainly have stated that it no doubt 

 exists, and is the cause of the pink and red tints often observed, 

 especially in fibrous gypsum. At one quarry, at Wentworth, 

 Hants county, there is found a deep-red crystalline gypsum. 

 With reference to the bituminous matters, I on one occasion 

 analyzed a nearly black gypsum from near Walton, Hants 

 county, with the following results : — 



Gypsum 80*45 



Anhydrite ........ 2"84 



Bituminous matter 1'53 



Clay and sand 7*94. 



Carbonates of lime and magnesia, 



with alumina and oxide of iron . 7 23 



100-00 

 Interesting additional facts are given by Dr. Dawson, who 

 mentions that at Gay's River, Colchester county, a very sin- 

 gular bed of gypsum exists containing pure quartz-sand, and 

 also that he has in his cabinet a specimen of gypsum from Cape- 

 Breton enclosing a crystal of mispickel. 



With reference to the formation of gypsum from anhydrite, 

 Dr. Dawson has long suspected, from the unusually disturbed 

 condition of the beds near those of gypsum, that part of this 

 rock, at least, may have resulted from absorption of water by 

 anhydrite, or some similar process involving increase of bulk ; but, 

 owing to the obscurities caused by denudation and the unequal 

 erosion of the gypsum, he has not been able to satisfy himself 

 fully on the subject. The whole question as to how the beds of 

 anhydrite could have been formed he thinks well worthy of study. 



XXIV. On the Integration of the General Linear Partial Dif- 

 ferential Equation of the Second Order. By R. Moon, M.A., 

 Honorary Fellow of Queen's College, Cambridge^. 



I 



N a former paper % I pointed out the criteria which must be 

 satisfied in order that the equation 



Q — Ti iQ _|T \ Y (~\) 



dx 2 dx dy dy 2 • • • w 



* Chemical News, vol. iv. p. 16. t Communicated by the Author. 



% Phil. Mag. for February 1868. 



