the 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



FEBllUAE'Y 1846. 



1 



XVI. On the Application of the Photographic Camera to Me- 

 teorological Registration. By Henry Collen, Esq.* 

 [With a Plate.] 



N April 1844, Mr. Ronalds applied to me for the purpose 

 of obtaining some photographic representations of figures, 

 forming " a sort of pictorial register of atmospheric electri- 

 city " upon glass plates coated with Canada balsam, which 

 figures had been executed at the Kew Observatory by means 

 of his electrograph, described in the Fourteenth Report of the 

 British Association. The desired result was quickly obtained 

 by the usual photogenic process, and also by the camera; the 

 latter being found however, as was to be expected, the greatly 

 superior mode. Several other impressions were afterwards 

 made from figures on coated metallic plates, some of which 

 were shown attached to Mr. Ronalds' s report to the meeting 

 at York. The sharpness and delicacy of the positive impres- 

 sions thus obtained gave rise to some experiments, made by 

 us conjointly, for the purpose of applying the photographic 

 camera to the registration of Volta's electrometer, the ther- 

 mometer, and the siphon barometer. The projection of sha- 

 dows on photographic paper, which, by the way, had been 

 already proposed and tried by several persons, was at once 

 objected to by Mr. Ronalds, whose knowledge of the delicacy 

 required in observing and registering the various instruments 

 at the Observatory, made him fully aware of the necessity of 

 obtaining as perfect definition as the best optical arrange- 

 ment would produce; an excellent compound lens, made and 

 kindly lent to us by Mr. Ross, was therefore used, and has 

 been employed on each of the instruments, i. c. the electro- 



* Communicated by the Author. 

 Phil. Mag. S. 3. Vol. 28. No. 185. Feb. 1846. G 



