835 Scientific NerDs^ Accounts of Books, ^c» " 



Notejfrom a Correfpondent refpeBing the Bokgnian Phofphorus, 



To Mr. NICHOLSON. 

 SIR, 



A AM In pofleffion of fome ftones from Monte Paderno, near Bologna, of which the 

 phofphorus, called there Spongia di luce, and Pietra cuminabile, is made. I have con- 

 fulted all the books of chemiftry which mention the method of making this phofphorus 

 and feveral experienced chemifts have exaftly followed their direftions, but in vain, as no 

 one has been able to caufe the ftone to imbibe light. 



Your inferting this in your valuable Journal, may perhaps be the means of procuring 

 fome information on the fubjeft, and the exaft method of preparing it ; likewife if it can 

 be procured in London. I brought fome from Bologna fome years ago, but it foon loft its 

 property of retaining light. 



I am, Sir, 



Your humble Servant, 

 Sept. 24, 1800. , R. T. 



EytraBofa Letter from Mr William Henry, dated Sept. 25, i8oo, to correct an Inference in 



his Paper on Galvanifm. 



" The inference which I had drawn, from the experiments defcribed in your Journal 

 for Auguft, refpeftlng the decompofition of the vegetable alcali, I had found to be erro- 

 neous, before the interefting fa£ls of Mr. Davy were known to me ; and I had fully in- 

 tended a recantation, along with an account of fome other experiments on the fame fub- 

 je£l, in which I was engaged, above a month ago. Thefe, however, various circum- 

 ftances have prevented me from completing ; and I think it proper, therefore, not to delay 

 making an acknowledgment, and ftating the caufe, of my miftake. 



" The fa£l: which firft led me to fufpeft, that I had drawn too hafty a conclufion,-was, 

 that the black precipitate proved, on examination, to be merely a metallic oxide, and not 

 charcoal, as I had fuppofed probable. Varying, therefore, the circumftances of the ex- 

 periment, I tranfmitted the galvanic influence through liquid cauftic alkali, without the 

 contaft of mercury , and the black powder then ceafed to appear. The gafes alfo turned 

 out to be a mixture of hydrogen and oxygen, in the proportions, pretty nearly, that might 

 be expefted from water. This oxygen, the imperfedl metals, contained in the quick- 

 Clver, had before prevented from appearing in a gafeous form. From ammonia, the con- 

 ta£l: of mercury being excluded, gafes were obtained correfponding, in kind and propor- 

 tion, with thofe ftated in your Journal (p. 261), the quantity of oxygen gas appearing to 

 diminifh as the alcaline folution was more completely faturatsd." 



