Isaac lloberts. 357 



Messrs. Roberts & Robinson. After a successful career as builders for 

 a quarter of a century, the firm gave up business in 1888, and thus 

 left Isaac Roberts in possession both of the means to provide himself 

 with the best scientific instruments and the leisure to devote himself to 

 their employment. 



Some years before the name of Dr. Roberts became known to the 

 scientific world, the present writer remembers hearing the late Earl of 

 Rosse remark on the many instances he knew of men who, after a 

 successful business career as builders, devoted a well-earned retirement 

 to practical astronomy. It is interesting to note that yet another 

 builder, of whom Lord Rosse had never heard, was destined to develop 

 and carry onwards to an unanticipated importance Lord Rosse's own 

 brilliant discovery of spiral nebulae. 



Though when at business Isaac Roberts worked with unremitting 

 diligence and pains, he still found time to supplement an education 

 which, in his earlier years, had been somewhat scanty. The result 

 was that he became a recognised master of his craft as a builder. 

 Roberts was, indeed, so much esteemed by his associates that his aid 

 was frequently invoked as arbitrator in disputes where technical 

 matters in building were involved. 



At the commencement of his scientific work Roberts devoted him- 

 self principally to geology. The first paper he wrote was in 1869 on 

 the Wells and Water of Liverpool, and in the following year he became 

 a Fellow of the Royal Geological Society. In 1878 he read a paper 

 at the British Association on the Filtration of Water through Triassic 

 Sandstone, and it was in this year that he commenced his career as a 

 practical astronomer. 



As to the astronomical equipment with which Dr. Roberts accom- 

 plished his work, reference may be made *o the interesting account 

 given by Mr. W. S. Franks in " The Observatory," for August, 1904. 

 Roberts commenced practical observation in 1878 with a 7-inch 

 refractor by Cooke, which was erected at his residence, 26, Rock 

 Park, Rock Ferry the same home, it may be noted, which Nathaniel 

 Hawthorne occupied when American Consul at Liverpool. In 1882 

 he moved his residence to Kennessee, Maghull, near Liverpool. In 

 1883 Roberts tells us that he made experiments in photographing 

 stars with ordinary portrait lenses, varying in aperture between 

 fths of an inch and 5 inches. The most efficient of these was 

 one of 2 inches aperture by Lerebours & Secretan, and he used this 

 as a standard for comparison with the others. The comparisons were 

 made by attaching the cameras to the declination axis of the 7-inch 

 refractor, and taking simultaneous photographs of well-known groups 

 of stars under precisely similar conditions. 



