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SCIENCE 



[N. S. Vol. XLIX. No. 1259 



tory was devoted to it. The establishinent 

 of a standard system of photographic mag- 

 nitudes proved a difficult and intricate 

 problem, bnt again the results are of pri- 

 mary importance, for the color oif a star, 

 which is best measured by the difference 

 between its visual and photographic mag- 

 nitudes, proves to be almost as important as 

 its spectral type, to which it is very inti- 

 mately related. Here again the principal 

 work 'of observation was done by others — 

 Miss Leavitt, Professor Bailey and Pro- 

 fessor King — ^btit the unifying guidance 

 was Pickering's. Closely related to this is 

 the discovery of variable stars, which, 

 previously largely a matter of chance, was 

 reduced to a system, whether by the com- 

 parison of plates of the same field taken at 

 different times, or by means of certain spec- 

 tral peculiarities. The new methods were 

 so successful that the mimlDer of variable 

 stars discovered at Harvard within a few 

 years was three times as great as that of 

 all those detected by all the astronomers of 

 the world during the previous hisitory of 

 the science. 



Finally, and by no means least, should 

 be recorded his deep interest in, and sup- 

 port of, cooperation between the whole fra- 

 ternity of astronomers, whether in this 

 country or abroad. There was hardly an 

 organization for the furtherance of any 

 specific astronomical aim, such as the Com- 

 mittee on the "Carte du Ciel" or the Solar 

 Union, in which he did not take an active 

 part, and his counsel and advice were al- 

 ways of weight. But equally influential, 

 though less conspicuous, was his ever gen- 

 erous aid to individual investigators, to 

 whom he was continually transmitting in- 

 valuable material from the treasures under 

 his charge, sometimes observatio'ns already 

 made, but unpublished, and again data con- 

 cerning stars which had been put upon his 

 observing lists for that especial purpose. 



His abiding willingness to use his powerful 

 influence to aid other astronomers in ob- 

 taining instruments for the expansion of 

 their researches, or funds to provide assist- 

 ance in the reduction and publication of 

 their observations, is known to all. 



It may be pardonable to speak of one or 

 two instances. In conversation, referring 

 to the Metcalf Telescope, for which he had 

 found the funds to purchase the glass disks 

 for the lens, and provide the moi;nting, 

 while the figuring of the lens was done, as 

 a labor of love and in his spare time, by the 

 distinguished amateur whose name it bears, 

 ' ' I felt as if a great artist had said to me 

 ' If you will buy the canvas, and the brushes 

 and paint, I will paint you a picture. ' ' ' 



If a more personal allusion may be ex- 

 cused, it may be recorded that, shortly after 

 the writer's first interview with Professor 

 Pickering (during which he had described 

 his first serious astronomical work, on 

 stellar parallax) a letter arrived from Har- 

 vard, saying in substance "I think that it 

 would be useful to determine the magni- 

 tudes and spectra of all your stars. If you 

 will send me a list of them, we will have 

 them oTjserved, and send you the results." 

 This involved the photometric and spectro- 

 scopic observation of some three 'hundred 

 stars (the photometric settings being made 

 by Professor Pickering himself) and was 

 offered as an unsolicited contribution to the 

 work of a young and unknown instructor ! 



The Harvard Observatory never admitted 

 graduate students of the ordinary sort ; and 

 doctoral theses are absent from the long 

 list of its publica:tions. But, under Pick- 

 ering, it was an educational center of the 

 first rank, and its pupils were not the im- 

 mature students, but the working astron- 

 omers of the country. Who among us has 

 not gone to Harvard, enjoyed the delight- 

 ful 'hospitalitj^ and finished courtesy of the 

 director, and returned, loaded down with 



