192 Mr. J. Spiller : Photographic Observations of 



There yet remain several results of great interest, which follow 

 from what has been done in the preceding articles ; but they 

 must be deferred for a while, as at the present time other en- 

 gagements press upon me. 



Sheffield, July 25, 1860. 



XXIV. Photographic Observations of the Solar Eclipse, July 18, 

 1860. By John Spiller, F.C.S.* 



ON the occasion of the late solar eclipse, July 18th, the equa- 

 torial telescope belonging to the Royal Artillery Institution, 

 Woolwich, was through the kindness of Captain E. J. Bruce, 

 R.A., placed at my disposal, and an opportunity thus afforded 

 me of attempting the photographic representation of the solar 

 disc as it appeared from this station under the several phases of 

 partial eclipse. The successful termination of the day's labour, 

 resulting in the production of twenty-three photographic im- 

 pressions of the phenomenon in its consecutive phases, appeared 

 to justify a descriptive account of the general arrangement of 

 the apparatus and the mode of operating, which it is hoped will 

 possess some degree of scientific interest. 



From previous experience in connexion with the similar event 

 of March 15th, 1858f, when the same telescope was employed, it 

 was found necessary to modify on the present occasion the dis- 

 position of apparatus then adopted ; and particularly to restrict 

 the admission of the solar rays by the substitution of a very 

 much smaller diaphragm for the large aperture then rendered 

 necessary by the unfavourable state of the weather. 



The telescope, with its portable stand provided with means of 

 adjustment in altitude and azimuth, was, on the 18th of July, 

 erected in the open air within the enclosures of the Royal Mili- 

 tary Repository on Woolwich Common, and immediately con- 

 tiguous to all the appliances of a well-furnished photographic 

 laboratory. The object-glass, 4 inches in diameter, has a 

 sidereal focus of 77 inches, and gives a representation of the 

 sun's disc measuring, at this season of the year, *7 inch in 

 diameter. For photographic purposes the eyepiece was removed 

 from the telescope, and a small sliding-bodied camera adapted to 

 the end of the tube ; it was then easy to project upon the ground 

 glass a perfectly denned image of the solar disc, using the means 

 of adjustment which the camera afforded for the purpose of 

 obtaining the best optical focus ; and in this plane the prepared 



* Communicated by the Author. 



t Vide Journal of the Photographic Society, April 21, 1858. 



