1909] Solar Vortices and Magnetic Fields, 615 



WEEKLY EVENING MEETING, 



Friday, May 14, 1909. 



His Grace the Duke of Northumberland, K.G. P.C. 

 D.C.L. LL.D. F.K.S., President, in the Chair. 



Professor George E. Hale, LL.D. Sc.D. For. Mem. R.S., 

 Director of the Mount Wilson Solar Observatory of the 

 Carnegie Institution of Washington. 



Solar Vortices and Magnetic Fields. 



I HEARTILY appreciate the privilege of describing in this lecture- 

 room some of the recent work of the Mount Wilson Solar Observatory. 

 Like so much of the scientific research of the present day, it goes 

 back for its origin to the fundamental investigations of English men 

 of science. The spectroheliograph, which tells us of the existence of 

 solar vortices, is a natural outcome of the application of the spectro- 

 scope in astronomy, where Englishmen were foremost among the 

 pioneers. The detection of a magnetic field within these vortices 

 followed directly from Zeeman's beautiful discovery of the influence 

 of magnetism on radiation — a logical extension of the earlier work 

 of Faraday — and from the classic investigations of Crookes and 

 Thomson on the nature of electricity. In reviewing these great 

 advances, investigators in other lands must again and again wonder 

 at the exceptional ability of the English mind to make fundamental 

 discoveries. When these discoveries have been made, it is a com- 

 paratively simple matter to utilise them in many departments of 

 science. Americans cannot fail to rejoice that they may share in 

 the traditions of a race which counts among its members the men 

 who have given the Royal Institution its fame. 



It is customary to distinguish sharply between the observational 

 and experimental sciences, including astronomy in the former. In 

 physics or chemistry the investigator has the immense advantage of 

 being able to control the conditions under which his observations 

 are made. The astronomer, on the other hand, must be content to 

 observe the phenomena presented to him by the heavenly bodies and 

 interpret them as best he may. I wish to emphasize the fact, how- 

 ever, that the distinction between these two methods of research is 

 not so fundamental as it may at first sight appear. In 1860 a 

 laboratory in which experiments were conducted for the interpretation 

 of astronomical observations was estabhshed by Sir William Huggins 

 on Upper Tulse Hill. The advantage of imitating celestial pheno- 

 mena under laboratory conditions was thus appreciated half a 

 century ago. I shaU indicate later how important a part such a 



Vol. XIX. (No. 103) 2 s 



