104 Mr. David Gill [May 23, 



Before closing this lecture I wish briefly to allude to another 

 engine of research in sidereal astronomy which quite recently has 

 received an enormous development, and whose application appears 

 to oflfer a rich harvest of results. I refer to the application of 

 photography to astronomical observation. 



Your respected member, Mr. De la Eue, is the father of this 

 method. Time does not permit me to dwell on his early endeavours 

 and his successful results, but they are well known to you all. He 

 opened up the field, and he cleared the way for his successors. 



The recent strides in the chemistry of photography and the pro- 

 duction of dry plates of extreme sensibility, have permitted the 

 application of the method to objects that formerly could not be 

 photographed. Here, on the screen, are the spectra of stars photo- 

 graphed directly from the stars by Dr. Huggins, the lines which tell 

 of the chemical constitution and temperature of the star's atmosphere 

 being sharply defined. 



Here are photographs of the great comet of 1882, which, with the 

 co-operation of Mr. Allis of Mowbray, I obtained at the Cape, by 

 attaching his ordinary camera to an equatorially mounted telescope, 

 and with its aid following the comet exactly for more than two hours. 

 Each one of the thousands of points of light that you see is the 

 picture of a fixed star. The photograph suggests the desirability 

 of producing star maps by direct photography from the sky. 



Here on the screen is a photograph of the great nebula of Orion, 

 or rather a series of photographs of it, made by Mr. Common of Ealing. 

 You will note the gradual development of detail by increase of ex- 

 posure, and the wonderful amount of detail at last arrived at. Here 

 are photographs from drawings of the same, and you will note the 

 discrepancies between them. And here is a photograph of a star 

 cluster, also by Mr. Common. 



No hand of man has tampered with these pictures. They have a 

 value on this account which gives them a distinct and separate claim 

 to confidence above any work in which the hand of fallible man has 

 had a part. 



The standpoint of science is so different from that of art. A picture 

 which is a mere copy of nature, in which we do not recognise some- 

 what of the soul of the artist, is nothing in an artistic point of view ; 

 but in a scientific point of view the more absolutely that the indivi- 

 duality of the artist is suppressed, and the more absolutely a rigid 

 representation of nature is obtained, the better. 



Here is a volume compiled by one of the most energetic and able of 

 American astronomers — Prof. Holden. It contains faithful reproduc- 

 tions of all the available drawings that have been made by astronomers 

 of this wo-.derful nebula of Orion from the year 1656 to recent 

 times. 



If now we were to suppose one hundred years to elapse, and no 

 further observation of the nebula of Orion to be made in the interval ; 

 if in some extraordinary way all previous observations were lost, but 



