DRIFTING LIGHT- WA VES. 97 



which was purchased by Mr. W. Spottiswoode, and by him 

 lent to Mr. Huggins for the express purpose of dealing with 

 the task Secchi had set spectroscopists. It did not, how- 

 ever, afford the required evidence. Huggins considered the 

 displacement of dark lines due to the sun's rotation to be 

 recognizable, but so barely that he could not speak con- 

 fidently on the point 



There for a while the matter rested. Vogel made ob- 

 servations confirming Huggins's results relative to stellar 

 motions; but Vogel's instrumental means were not suffi- 

 ciently powerful to render his results of much weight. 



But recently two well-directed attacks have been made 

 upon this problem, one in England, the other in America, 

 and in both cases with success. Rather, perhaps, seeing 

 that the method had been attacked and was supposed to 

 require defence, we may say that two well-directed assaults 

 have been made upon the attacking party, which has been 

 completely routed. 



Arrangements were made not very long ago, by which 

 the astronomical work of Greenwich Observatory, for a long 

 time directed almost exclusively to time observations, should 

 include the study of the sun, stars, planets, and so forth. 

 Amongst other work which was considered suited to the 

 National Observatory was the application of spectroscopic 

 analysis to determine motions of recession and approach 

 among the celestial bodies. Some of these observations, 

 by the way, were made, we are told, " to test the truth 

 of Doppler's principle," though it seems difficult to suppose 

 for an instant that mathematicians so skilful as the chief 

 of the Observatory and some of his assistants could enter- 

 tain any doubt on that point Probably it was intended 

 by the words just quoted to imply simply that some of 

 the observations were made for the purpose of illustrating 

 the principle of the method We are not to suppose that 

 on a point so simple the Greenwich observers have been in 

 any sort of doubt 



At first their results were not very satisfactory. The 



H 



