78 president's address — section a. 



the camera in the ordinarj' way, and exposed for seven seconds. 

 The picture was about an inch long, and bore enlargement to same 

 extent. Mr. IJpherwood used a portrait lens of very short focus on 

 a hill 700ft. high. Still the great difference between his exposure 

 and those of Mr. De La Rue is not easily accounted for, although 

 manv accepted Mr. Usherwood's picture as the first one ever made 

 of a comet. 



We are told"^ that in his photographs of the moon and other 

 objects Mr. De La Rue iised a negative collodion containing iodide 

 of cadmium and avoided acetic acid and alcohol in the bath, which 

 he made as neutral as possible. In this way he obtained photographs 

 of full moon, either instantaneously or in five or six seconds, and in 

 its half phase in twenty to thirty seconds.^" Early^^ in 1859 Mr. 

 De La Rue had the courage to propose, and the ability finally to 

 carry out, the transfer of the Kew photo-heliograph to Spain in 1860, 

 in order to photograph the total eclipse of July 18tli in that year. 

 It was a bold experiment, and was crowned with success. In esti- 

 mating the conditions we must remember that he had no chance of 

 finding ovit beforehand the time of exposure for red jjrominences. 

 Two photographs of the totality were secvired ; each had an 

 exposure of one minute, and each showed the red prominences 

 clearly, and served for ever to set at rest the much vexed question 

 of those days, viz., Avhether they belonged to the sun or the moon, 

 for the photographs proved definitely that the red prominences 

 belonged to the sun. Mr. De La Rue's station was at Rivabellosa, 

 in Spain, and on the Mediterranean coast of Spain, 240 miles from 

 Rivabellosa, Father Secche^'^ had set up his observatory, and took 

 photographs v.dth a 9in. refractor on a smaller scale than those 

 taken by Mr. De La Rue, but they fully confirmed the results obtained 

 by the English party — that the prominences belonged to the sun. 



In the first photograph taken at Rivabellosa there was to be 

 seen to the east of the sun a totally detached prominence or 

 cloud of curved or boomerang form, and in the second this was 

 partly covered by the advancing limb of the moon, and a fresh 

 lot showed themselves on the other side. The light of the red 

 prominences was estimated to be photographically 1 80 times 

 brighter than that of the moon.^^ 



On 27th of February, 1863^*, and on 3rd March of the same 

 year. Dr. Huggins led the way in photographing star spectra, 

 and found that when the spectrum of Sirius was caused to fall 

 upon a sensitive collodium surface an intense photographic spectrum 

 of the more refrangible part was obtained ; but, " from want of 

 accurate adjustment of the focus, or from the motion of the star 

 not being exactly compensated by the clock movement, or from 

 atmospheric tremors, the spectrum, though tolerably well defined 

 at the edges, presented no indication of lines." 



Rutherford^^ began his work in lunar photography in 1858 

 Math an equatorial 11 ^in. aperture and 14ft. focal length. Finding 



