1(5 president's address. 



Aslronoiiij/. — A biologist may well refuse to offer any remarks on his 

 own authority in regard to this earliest and grandest of all the sciences. 

 I will therefore at once say that my friend the Savilian Professor of 

 Astronomy in Oxford has turned my thoughts in the right direction in 

 reward to this subject. There is no doubt that there has been an immense 

 'revival' in astronomy since 1881 ; it has developed in every direction 

 The invention of the ' dry plate,' which has made it possible to apply 

 photography freely in all astronomical work, is the chief cause of its great 

 expansion. Photography was applied to astronomical work before 1881, 

 but only with difficulty and haltingly. It was the dry-plate which made 

 long exposures possible, and thus enabled astronomers to obtain regular 

 records of faintly luminous objects such as nebulre and star-spectra. 

 Roughly speaking, the number of stars visible to the naked eye may be 

 stated as eight thousand : this is raised by the use of our best telescopes 

 to a hundred million. But the number which can be photographed is 

 indefinite and depends on length of exposure : a thousand million can 

 certainly be so recorded. 



The serious practical proposal to ' chart the sky ' by means of photo- 

 graphy certainly dates from this side of 1881. The Paris Conference of 

 1887, which made an international scheme for sharing the sky among 

 eighteen observatories (still busy with the woi'k, and producing excellent 

 results), originated with photographs of the comet of 1882, taken at the 

 Cape Observatory. 



Professor Pickering, of Harvard, did not join this co-operative scheme, 

 but has gradually devised methods of charting the sky very rapidly, so 

 that he has at Harvard records of the whole sky many times over, and 

 when new objects are discovered he can trace their history backwards for 

 more than a dozen years by reference to his plates. This is a wonderful 

 new method, a mode of keeping record of present movements and 

 changes which promises much for the future of astronomy. By the 

 photographic method hundreds of new variable stars and other 

 interesting objects have been discovered. New planets have been 

 detected by the hundred. Up to 1881 two hundred and twenty were 

 known. In 1881 only one was found ; namely, Stephania, being 

 No. 220, discovered on May 19. Now a score at least are discovered 



on this occasion impossible, and, moreover, tlie patience of even the general meeting 

 of the British Association cannot be considered as unlimited. With a view to the 

 preparation of a more detailed review, I had asked a number of friends and col- 

 leagues to send me notes on the progress and tendency in their own particular 

 branches of science. They responded with the greatest generosit}' and unselfisliness. 

 I must entirely disclaim for them any responsibility for the brief detached state- 

 ments made in the address. At the same time I should wish to thank them here by 

 name for their most kind and timely help. They are : Sn- VVilUam Ramsay, 

 Mr. Soddy, Professor H. H. Turner, Dr. Marr, Dr. Haddon, Dr. Smith Woodward, 

 Professor Sherrington, Professor Farmer, Professor Vines, Dr. D. H. Scott, Pro- 

 fessor Meldola, Mr. Macdougal, Professor Poulton, Mr. C. V. Boys, Major MacMahon, 

 and Mr. Mackinder. 



