352 Improvement in Photography. 



Carbonate of lead, 



Sulphnret of zinc, 

 gj f Oxide of iron, 

 §3 J Silica, 

 g I Alumina, . 

 O L Magnesia, . 



100.433 

 Note to No. 2. — William M. Uhler tried approximately the pro- 

 cess of amalgamation with No. 2, suffering the mercury to re- 

 main in contact with the pulverized ore for several days, and 

 found that 1 lb. avoir, took up 419 grs. troy, which gave 145 lb. 

 5 oz. 16 dwt. 16 grs. to the nett ton avoirdupois of 2000 lbs. 



Art. X. — Improvement in the Daguerreotype process of Pho- 

 tography ; by F. A. P. Barnard, Prof, of Math, and Nat. Phil, 

 in the Univ. of Alabama. 



Messrs. Editors, — I commenced, about a year since, in con- 

 nection with Dr. Wm. H. Harrington of this place, a series of 

 experiments in photography, according to the methods of Mr. 

 Fox Talbot and M. Daguerre. Our attention was directed 

 principally to the Daguerreotype process. From the analogies 

 known to exist between iodine and chlorine, we were strongly 

 impressed with the belief that the latter substance might in 

 some manner be employed to render the surface of silver more 

 sensitive to the action of light than it had yet been made. To 

 determine the correctness of this opinion we instituted a va- 

 riety of experiments, which, as they proved for the most part 

 unsuccessful, it is unnecessary to detail. The coating formed 

 by the direct action of chlorine gas upon polished silver, was 

 not found to possess the desired photogenic properties. We 

 were led, therefore, to seek whether by the decomposition of 

 some compound of the metal, a sensitive chloride could not be 

 produced. Mr. Talbot had already done this in the preparation 

 of his photogenic paper ; but as it was our desire to avail our- 

 selves of the beautiful lights formed by the vapor of mercury, 

 and as the prepared paper, at least so far as our experiments go, 

 is not susceptible of receiving them, we endeavored to produce 



