Prof. Gmclin^s J-hutlysts. 3i'j 



beam,''' and with all due deference, I would inquire, what is 

 the difference between this wezw apparatus, either in principle 

 or in application, and the old fashioned contrivance for dis- 

 tinguishing between a true and a counterfeit guinea ? I con- 

 fess (hat I ow sec none, ex« ept that the fornner is a more 

 improved instrument, and the latter was limited to weighing 

 guineas and half guineas only, in air and in water ; but the 

 fact that a similar machine was in use years ago, does not in 

 my estimation dimmish the credit due to Mr. Patten for his 

 invention. 



With great regard, 



Your obt, servant, 



S. F. DANA. 

 Hanover, N. H., March 18th 1825. 



Art. XVIII. — Analyses^of several minerals^ by Prof. Gmehn, 

 of the University of Tubingen, Communicated by Jeremiah 

 Van Rensselaer, M. D. 



Prof. Silliman, 



Dear Sir, 

 I HAVE much pleasure in offering you an extract of a letter 

 just received from my friend Prof. Gmelin, dated, '' Univer- 

 sity of Tubingen in Wurtemberg, Jan. 6th, 1825." 



Yours truly, 



JER. VAN RENSSELAER, 

 New- York, Apil 21st, 1825. 



" Since n y last to you T have been much occupied with 

 analvs;-, a shall give you some of the results obtained, 



"ihavc discovered a beautiful mica in large lariiiiise to be 

 a crystallized Lepidolite — that is to say, to contain lithion, 

 It is c« mposed of 



Silica, « - .. _ 52.254 



Alumina, - - - - 28,345 



Ox. of Manganese, - - 3.602 



Potash, - - - . 6.903 



Lithion, ^ , . . 4,792 



Fluoric Acid, - - - 3.G09 



99.505 

 Vol. IX. -No. 2. 42 



