Isaac Roberts. 361 



" The photographs by Common of the great nebula in Orion were 

 epoch-making in astronomical photography, and worthily was the 

 medal bestowed on him for his classic work, and it is no disparagement 

 of the labours of the present recipient (Roberts) if one traces in them 

 the mark of what Common had shown to be possibilities." 



Perhaps the most famous of Dr. Roberts' photographs was that of 

 the great nebula in Andromeda. This plate it was which first fully 

 illustrated the capabilities of photography for the representation of 

 nebulae. Even after the lapse of 15 years it may still be doubted 

 whether any more beautiful representation of any celestial object has 

 ever been produced. Of this Sir W. Abney said in the address just 

 referred to : 



" In December, 1886, Roberts produced a photograph of the nebula 

 in Orion with his 20-inch reflector with an exposure of 15 minutes, and 

 almost exactly 10 years after he produced a photograph of the same 

 object with an exposure of 81 minutes, and introduced us to nebulosi- 

 ties in the surrounding parts which were unsuspected before. ... A 

 little afterwards he produced hi? recently published photograph of the 

 great nebula in Andromeda, giving an exposure of 4 hours to the plate. 

 In this prolonged exposure we have an example of a triumph of 

 patience and of instrumental perfection, though these qualities are 

 exhibited in other instances as well. This beautiful object is depicted 

 with its rings of nebulosity in great perfection, and we can correct the 

 eye observations which had previously been made upon it. The stars 

 in the field are beautifully sharp and round, showing that the eye as 

 well as the instrument had to be employed throughout that long 

 exposure to correct changes in the position of the star due to atmos- 

 pheric refraction, and variation in the rate of clock-driving." 



Notwithstanding all his later successes with the spiral nebulae, 

 Roberts always considered the Andromeda picture as his most notable 

 achievement. In the fine portrait of him which was executed shortly 

 before his death by his wife's sister, the favourite pupil of Rosa 

 Boriheur, Roberts is represented resting in an arm-chair, and holding in 

 his hand one of his memorable photographs. The plate which he chose 

 was that of the great nebula in Andromeda, taken 15 years before. 

 With consummate skill the artist has reproduced in an oil painting 

 mwch of the delicacy and beauty which give that picture its charm. 



In 1896 Dr. Roberts was one of the party who went to Vadso in 

 the steamship " Norse King " to observe the total eclipse of that year. 

 The eclipse itself was disappointing, but the circumstance deserves 

 record from the fact that among those on board was Mademoiselle 

 Dorothea Klumpke, D.Sc., of Paris Observatory, herself an earnest and 

 distinguished worker in astronomical science. The acquaintance thus 



