304 Sir Howard Grubb [May 25, 



WEEKLY EVENING MEETING, 



Friday, May 25, 1894. 



William Huguins, Esq. D.C.L. LL.D. F.R.S. Vice-President, 

 in the Chair. 



Sm Howard Grubb, F.E.S. F.R.A.S. 



The Development of the Astronomical Telescope. 



Since I last had the honour of lecturing in this theatre, astronomical 

 research has had opened up to it a totally new field of work, one 

 which appears almost without limit in its scope. 



When Dr. Gill, of the Cape of Good Hope Observatory, made 

 arrangements to photograph the comet of 1882 with a long exposure, 

 using only an ordinary photographic lens, even his fertile and 

 sanguine spirit did not, I think, anticipate the possibilities opened 

 to astronomical research since photography has been called in to 

 its aid. 



I do not propose in this lecture to discuss any of the interesting 

 astronomical ancl physical problems that have been opened up by 

 the adoption of the " New Astronomy," as it is aptly called. I leave 

 these subjects to be dealt with by those who have made such their 

 special study, and are better qualified to speak of them. 



I propose to-night to discuss the differing conditions which astro- 

 nomical instruments are required to fulfil under the new system as 

 compared with the old, and to point out the possibilities that appear 

 to exist for improvement and future development, touching only on 

 the astronomical part of the work so much as may be necessary to 

 explain the instrumental equipment required. 



It would be well, perhaps, that I should first call to your recollec- 

 tion some of the chief lines of work which have been opened by the 

 introduction of the new photographic method. 



The International Photographic Survey of the Heavens has been 

 undertaken by sixteen of the principal observatories of the world, 

 which have agreed to co-operate in producing two series of photo- 

 graphic pictures of the entire heavens ; the first series including all 

 stars down to the 11th magnitude, a catalogue of which is to be 

 formed from the photographic plates; while the other series will 

 include all stars to the 14th magnitude, and will be photographically 

 reproduced as a chart. 



The enormous advantages of photography for this work, as com- 

 pared with the old system, have been brought so often and so 

 prominently before you by Dr. Gill and other lecturers that it is 

 unnecessary for me to dwell upon them here. As a supplement to 



