57d SALINE, EFFLORESCENCE UPON WAILS, &C. 



I was performing fome experiments with Mr, Richard Da?- 

 ton, an ingenious leflurer in natural philoJTopby of this place, 

 with a pile compofed of GO pair of fix-inch plates of zinc and 

 Experiment rn copper, when it occurred to me to place a minute globule of 

 rffeOed?'^ "^^ mercury in an iron fpoon, refting on the top of the pile, and 

 to approach to it a thick iron wire conneded with the other 

 end of the apparatus; the etfeft was, that a brilliant ftar of 

 light was produced from the, mercury, attended with a crack- 

 ling noife and a copious emitSon of fparks ; the mercury was 

 found converted into the black oxide. , 



Tht dark co- The moft common fpecies of biliary calculus is that com- 

 '"."■"^n P"^'"^'" pofed of the peculiar cryftalline matter, which in fome of its 



*f gall ftones do '^ . r i i /- •,,.-, 



not app.-ar to he properties retembles ipermaceti, through which are inter- 

 Infpifated rcfin fperfed a number of dark coloured particles, that are fuppofed 

 to confi ft of hardened bile. This is the idea entertained by 

 M. Fourcroy,* and the one which I adopted, when I made 

 the experiments on this fubje6l which are related in the fourth 

 volume of your Journal. I have, however, fince that time 

 been difpofed to alter my opinion ; in two fpecimens of the 

 , biliary calculi, which I examined, after feparating the cryftal- 

 line matter by alcohol, I was unable to dilTolve the dark co- 

 loured particles by any menftruum which I applied to them; 

 they imparled a yellowifli tinge to water and other fluids, but 

 the great bulk of their fubftance remained unchanged. It is, 

 I conceive, not probable that the mere infpilTation of the retia 

 of the bile could fo far alter its properties. I mention this cir- 

 cumfiance principally with a view of attrafting the attention 

 of any of your readers who may be in polTeiEon of a number 

 of gall-ftones, fo as to afcerfain whether the untraftable nature 

 of thefe particles is a general property of the cyftic-adipo- 

 bilious concretions, or foraething peculiar to the fpecimens 

 upon which I experimented. 

 Meltjng pomt of ^ ^^'^ conclude this mifcellaneous letter with fome remarks 

 fpermaceti. upon the melting point of fpermaceti. In the paper to which 

 exoe'riment'con.^ have already referred, I mentioned the diverfity of opinion 

 films that ic is a that had been entertained on this fubje6l, and afterwards ftated 

 little above 112". ^j^^^ ^^ ^^^,^ experience induced me fo fix it at the 1 I2th de- 

 gree. Dr. Thomfon, in the firft volume of his Chemiftry, 

 fixes the melting point at I33°,t while in the fourth he llates 



* Syfteme, X, 59i f ^^ge 358, 



