498 Bev. S. J Perry [May 24, 



WEEKLY EVENING MEETING, 



Friday, May 24, 1889. 



Sir James Crichton Browne, M.D, LL D. F.E.S. Vice-President, 



in tlie Chair. 



The Eev. S. J. Perry, D.So. F.E.S. F.E.A.S. Director of Stonyhurst 

 College Observatory. 



The Solar Surface during the Last Ten Years. 



The solar surface is a subject on whicli so much has been written of 

 late years, that it would be highly unsatisfactory to attempt in one 

 short hour even a brief enumeration of the results obtained and the 

 theories advanced by the many eminent men who have devoted atten- 

 tion to this branch of solar physics. The end which I propose to 

 myself this evening, and which, I venture to think, is most in accor- 

 dance with precedent in these discourses, is to lay before you, in as 

 clear a manner as I am able, the results obtained at the observatory 

 to which I am attached, in so far as they enter into our present 

 subject, and to touch upon the work of others in such a manner only 

 as to complete the picture, by showing the bearing of our labours on 

 the general result. 



For the last ten years I have been anxiously endeavouring to 

 make Stonyhurst as efficient an observatory for solar physics as the 

 means at my disposal would admit, so I was naturally desirous not to 

 undertake any work that would be a mere repetition of what was being 

 done better elsewhere. From the outset, therefore, I excluded from 

 my programme a daily photograph of the sun, as this had been already 

 undertaken at the Eoyal Observatory, assisted by other Government 

 observatories in India and at Mauritius, and the most I could have 

 hoped for in this direction would have been to fill up a few gaps in 

 an almost perfect series. My choice, therefore, lay between drawings 

 made at the telescope by aid of a solar eye-piece, and the use of a 

 sketch-board on which the sun's image could be projected. The 

 object in view being to procure the most complete and faithful repre- 

 sentation of nature, I had no hesitation in rejecting all forms of 

 solar eye-pieces, as by this method of observation too much is left to 

 the imagination of the draughtsman ; although a solar prism is not 

 unfrequently of great advantage in supplementing other methods of 

 attack, especially when delicate details require verification. The 

 sketch-board, on the other hand, may be so used as to leave very little 

 indeed to the ideas or bias of the observer. To effect this the follow- 

 ing method has been adopted. A circle ten and a half inches in 



