1824.] Mr. Darnell's Reply to X. 439 



Article V. 



Reply to X. By J. F. Daniell, Esq. FRS. &c. 



(To the Editors of the Annals of Philosophy.) 



GENTLEMEN, Nov - 6 ' 1S24 - 



The illustration of your correspondent X. is so extremely 

 apposite, that I at once agree with him in thinking it conclusive. 

 I suppose, with him, " three barometer tubes standing in a 

 reservoir, and filled alike with mercury, but that one of the tubes 

 expands by heating, that another contracts, and that the third 

 neither expands nor contracts." But then, I pretend to say 

 (in defiance of the odium philosophorum), that if this apparatus 

 be exposed to various temperatures, the columns in all will not 

 rise to precisely the same height as measured upon their respect- 

 ive tubes. 



X. does me too much honour in supposing that I am the first 

 who ever used the fraction of the apparent dilatation of mercury 

 for correcting the observed height of the barometer : it has long- 

 been known to all those moderately acquainted with the subject, 

 that the expansion of the scale must be taken into account for 

 all nice purposes. 



I trust that X. will not wait for my visit to the Grampian 

 Hills to disclose his method of detecting "the most minute 

 impurity existing in mercury by inspection of a single drop of 

 that metal," but that he will be' induced, for the good of science, 

 to communicate so important a discovery to the Annals of Phi- 

 losophy* I remain, Gentlemen, faithfully yours, 



J. F. Daniell. 



Article VI. 



Account of a new Mineral Substance. By M. Levy, MA . of the 



University of Paris. 



(To the Editors of the Annals of Philosophy.) 



GENTLEMEN, Nov - 10 ' 1824 ' 



You will, perhaps, be able to spare room in the next number 

 of the Annals of Phitosoplu/ for a short description of a new 

 mineral substance, which Ipropose to name Rosehte, in honour 

 of Mr. Gustavus Hose, of Berlin. 



The only specimen where I have observed it belongs to Mr. 

 Turner's collection. It occurs in small well-defined translucent 

 crystals of a deep rose colour, on amorphous greyish quartz. 



* We concur heartily in th« wi»h expressed by our friend Mr. Daniell.— C« *id P' 



