314 Obituary Notices of Fellows deceased. 



carbon enlargement of this picture (taken on January 30, 1883, with 

 37 minutes' exposure), he modestly remarked of it that " although 

 some of the finer details are lost in the enlargement, sufficient remains 

 to show that we are approaching a time when photography will give 

 us the means of recording, in its own inimitable way, the shape of a 

 nebula and the relative brightness of the different parts in a better 

 manner than the most careful hand-drawings." He might well have 

 said that the time was already come, for the chief steps had certainly 

 been taken, and we may note with admiration that they had been 

 taken by a man who had only been able to devote himself to astronomy 

 seriously during the leisure of some half-dozen years. In that brief 

 period Common had realised the limitations of an 18-inch telescope, 

 which may be taken to represent the best instrument available at the 

 time for a man of moderate means ; had determined on the bold experi- 

 ment of doubling the diameter, and carried out the project successfully ; 

 and had assigned to the reflector that work of photographing the 

 nebulae which has come to be regarded as its chief function. All this 

 was not done without much hard work, and it is not surprising if the 

 pace was not maintained afterwards. An opportunity occurred for 

 selling the 3-foot telescope, and Common then deliberately took a 

 complete year's rest before commencing another astronomical enter- 

 prise ; though during this period the project of making a much larger 

 telescope still (mirror 5 feet in diameter) was already in his mind, and 

 plans were maturing. He had indeed, so early as 1880, determined to 

 have this telescope, and to make it entirely himself, and had ordered 

 a disc of glass for the purpose, but the instrument was not completed 

 till 1891. A full account of its construction is given in "Mem. 

 R.A.S.," vol. 50, and he was able to announce that " the power of the 

 5-foot over that of the 18-inch and 3-foot is proportionate to the size. 

 On nebulse this is seen to great advantage, both visually and photo- 

 graphically. Such an object as Mimas, which the 18-inch telescope 

 would, under the most favourable conditions, just render visible, and 

 the 3-foot show fairly well, can with the 5-foot be seen close to the 

 end of the ring, and away from it could not be overlooked." But this 

 satisfactory result was not attained without encountering many diffi- 

 culties. Of one grinding tool that he tried he reports : " The tool 

 was several months in preparation, but a very few minutes' work 

 sufficed to show that it was unworkable. The faces of the glass 

 squares caught the mirror and tore it up in places, but where this had 

 not occurred the surface produced by grinding glass on glass was all 

 that could be desired." Such failures might have discouraged a less 

 resolute man, but Common simply utilised them as lessons of great 

 value, and seemed actually to rejoice in them. " I consider it an 

 extremely fortunate circumstance," he writes, " that the first mirror 



