Miscellanies. 375 



detect any trace of the drawing. The sheet is now exposed to the va- 

 por of mercury, and when it has been heated to a temperature of 60 de- 

 grees of Reaumur, or 167 Fahr., the drawings come forth as if by en- 

 chantment. One singular and hitherto inexplicable fact in this pro- 

 cess is, that the sheet, when exposed to the action of the vapor, must 

 be inclined, for if it were placed in a direct position over the vapor 

 the results would be less satisfactory. The angle used is 48 degrees. 

 The last part of the process is to place the sheet in a solution of the 

 hyposulphite of soda, and then to wash it in a large quantity of dis- 

 tilled water. The description of the process appeared to excite great 

 interest in the auditory, amongst whom were many distinguished 

 persons connected with science and the fine arts. 



Unfortunately the locality was not adjusted suitably for the perform- 

 ance of M. Daguerre's experiments, but we understand that arrange- 

 ments will be made for a public exhibition of them. Three highly 

 curious drawings obtained in this manner were exhibited ; one of the 

 Pont Marie ; another of Mr- Daguerre's atelier ; and a third of a room 

 containing some rich carpeting, all the minutest threads of which were 

 represented witli the most mathematical accuracy, and with wonder- 

 ful richness of effect. — London Globe of 23d August. 



We have to add, that a professional gentleman in New York in- 

 formed us before the late arrival of the British Queen, (which brought 

 the first printed account of M. Arago's disclosure,) that he was in 

 possession of the secret, and in connection with an eminent chemist 

 in New York had already obtained beautiful results, but is not able as 

 yet fully to arrest them. 



The surface of the mercury should be as large as the plate. 



Practical difficulties are encountered in giving the mercury the 

 proper temperature and in avoiding- the corrosive vapors so distress- 

 ing to the eyes ; but we trust that these and all other difficulties will 

 be overcome, and that we may have the pleasure of announcing the 

 entire success of the ingenious experimenters. — Eds. 



52. Aurora Borealis of Sept. 3, 1839 — An auroral display of the 

 most magnificent character was seen throughout the country on the 

 night of September 3, 1839. An account of observations upon it at 

 various stations, will be given in our next number. 



53. Geological Surveys. — We have before us numerous reports on ge- 

 ological surveys, most of which were named at the close of Vol. xxxvi. 

 It has been found hitherto impossible to peruse and digest them intelli- 

 gently, and indeed the wide range of geological exploration in the various 

 states presents such voluminous details, that we are compelled to relin- 

 quish the effort to present even a condensed summary of them. This 



