[ 137 ] 



them, T poured on boiling water, thus by lixiviatlon to extraifl' 

 any faline matter from the earthy or lefs foluble parts. J fuffered 

 this mixture, repeatedly ftirred, to fubfide for about twelve hours 

 and the clear liquor decanted off, which had already a brackifh. 

 taiie, was foon evaporated down to a ftrong faline brine. 



In order to feparate the cryftallizable falts from the potajh^. 

 which under fuch circumftances would not cryflallize but re- 

 main in folution in the mother liquor, I fet this brine to cool ; 

 and, on examining it the following day, found an abundant crop 

 of beautiful cryftals, fliot out to a confiderable lize, a few of 

 which I have preferved for your infpecflion. 



The remaining liquor when evaporated to drynefs afforded a 

 faline mafs in confiderable quantity, which, from its flrong efFe£l 

 on vegetable blues, I ftill hoped might contain fome of the de- 

 fired alkali ; but on fubmitting it to the examination of my 

 ingenious and learned friend Mr. Higgins, he could not detedl 

 a particle of any kind of difengaged alkah\ though he fought 

 it by fome of the niceft tefts of modern chemiftry. I therefore 

 think we are founded in concluding, that nearly the whole mafs 

 of falts thus procured muft confift oi fulphat oi foda with little 

 or no intermixture. 



1 CONFESS, my dear Sir, that regarding this refult in a philo- 



fophical, but particularly in a geological point of view, it appears 



to me not a little fingular, that marine alkali combined with 



Vol. VIIJ. S . Jtilphurk 



