various Bodies imrmrfed in the Water ofDifs Mere. Jj 



« tninutely divided ftate, or progreffively during formation) has been depofited on bodies, 

 fuch as the flints when in contadl with the mud. But an excefs of fuiphur appears to be pre- 

 fent ; for, when copper is put into the Mere, the fuiphur readily combines with it ; and, at 

 the fame time, a fmall portion of iron appears to unite with the compound of copper and 

 fuiphur, poffibly by the mere mechanical a6l of precipitation. 



The incruftation on the copper wire and cuttings is, in every property, fimilar to that 

 rare fpecies of copper ore, called by the Germans hupfer fchwartine (cuprum ochraceuni 

 nigrum) y and I confider it as abfolutely the fame. In refped to the martial pyrites on the 

 flints, there can be no hefitation ; and, as in thefe two inftances, there were evident proofs- 

 cf the recent formation of ores iji the humid way, I was delirous to afcertain the efFodl on 

 filver. I therefore wrote to Mr. Wifcman, to requeft that he would take the trouble to 

 make the experiment ; and. received from him the following anfwer, accompanied by the 

 Ipecimens. 



« Sir, ** Difs, 8th of September, 1798. 



" Immediately upon the receipt of your letter (27th July), I laid fome filver plate, and 

 filver wire, into the Mere; the whole weighed 235.6 gr. I took it out on l-hurfday 

 laft (September 6th), and, after cleaning it carefully from mud and weeds, I find it weighs. 

 242.8 gr. ; an increafe of 7.2 gr. The filver plate you will find much tarniflied, in fome 

 parts almoft black ; the wire is in many places fairly incrufted, which cruft, upon the prefigure 

 of the fingers, comes off in thin fcales. The whole appearance of the filver ftrongly 

 indicates the prefence of fuiphur, which I have no doubt abounds in every part of the 

 Mere. The peculiar fmell of the mud gives me reafon to fuppofe, that a great deal of 

 hepatic air is produced ; which, probably, uniting with the iron held in folution in the 

 water of the Mere, may account for the martial pyrites found on the flints. By what affinity 

 the copper wire, laid in this water, is attacked, I am not chemift enough to determine. 



" I have begun a fet of experiments, with the view of producing the fame efFe<Sts upoiv 

 copper wire by artificial means ; but whether I ihall fucceed, I am not at able prefent to fay.. 



" I am, &c. 



" BENJ. WISEMAN."- 



P. S. By experiments I have lately made, I find hepatic gas precipitates carbonate of iron, 

 in the form of a black flocculent matter ; 7 J j>ai;ts of which are iron, and 29 fuiphur. 



The filver plate I found (as Mr. Wifeman has mentioned) much tarniflied,, and in many 

 places almofl: black, butl could not detach any part of it. I fucceeded better with the wire,. 

 and collefted a fmall portion of a black fcaly fubfl;ance, which, as far as the fmallnefs of 

 the quantity would allow it to be afcertained, was fulphuret of filver ;- and- was fimilar, in 

 every refpeft, to the fulphurated or vitreous ore of filver, called by the Germans glafertz. 

 This efFeft on the filver was to be expefted ; and I recolledl: to have read; not many months^ 

 ago, in one of the foreign journals, that Mr. Prouft had examined an incruftation, of a 



M2 dark 



