358 Obituary Notices of Fellows deceased. 



But the great step which he made may be given in his own words 

 (" Monthly Notices " of the Eoyal Astronomical Society, January, 

 1886): "The result of these experiments, and comparison with 

 Mr. Common's great photograph of the nebula in Orion, was that I 

 gave Sir Howard Grubb an order to make me a 20-inch silver-on- 

 glass reflector, with 100 inches focal length, the photographs to be 

 taken directly in the focus of the mirror, to obviate any loss of light 

 by a second reflection, the photographic telescope to be mounted on 

 the same declination axis as the 7-inch refractor, one being the counter- 

 poise to the other." In a foot-note he adds that " To Dr. Huggins is 

 due the credit for devising this most ingenious, simple and useful 

 mode of mounting a reflector and refractor side by side; and the 

 skill of Sir Howard Grubb is well shown in the arrangements of the 

 instrument to perform the objects intended." 



Mr. Franks records that "over a year was spent by Dr. Roberts in 

 minor alterations and perfecting details before the instrument could be 

 considered good enough to perform satisfactorily the work which was 

 expected of it. From that day to this with the exception that a 

 Calver mirror was substituted for the Grubb in 1888 and a 5-inch 

 Cooke camera added in 1895 the equipment remains the same as 

 originally planned by Dr. Roberts, a fact which speaks for itself as to 

 the patient forethought bestowed upon this pioneer instrument, which 

 has now become historically famous." 



One circumstance, however, it would ill become the present writer 

 not to record. Before ordering the 20-inch telescope from Grubb, 

 Dr. Roberts had obtained an 18-inch instrument from the same 

 maker. The results were so encouraging that he decided to enlarge 

 the equipment on the same principle as above mentioned. The 18-inch 

 telescope thus displaced, a most beautiful instrument, was then, with 

 characteristic generosity, presented by Dr. Roberts to the observatory 

 of Dunsink, co. Dublin. 



As to the relative merits of reflectors and refractors for celestial 

 photographic work, there has been much controversy, and in this 

 controversy Roberts, as might naturally be expected from his great 

 success, vigorously upheld the claims of the reflectors. As Mr. Franks 

 tells us, " Roberts was one of the earliest and most consistent advocates 

 of the merits of the reflector for celestial photography, and lived to see 

 his predilection confirmed in quarters where there had previously been 

 a strong prejudice for refractors. His views on the relative perform- 

 ance of camera lenses are well known, but it is not so well known that 

 he had a very perfect star-camera fixed on the tube of the 20-inch 

 reflector, with which all objects were photographed in duplicate, during 

 the last nine years ; and it was the unvarying superiority of the 



