154 CARNEGIE INSTITUTION 



this could be used in place of the larger outfit with resulting saving 

 in time and labor, and for much of the preliminary work and for the 

 laboratory investigations it would be decidedly more convenient. 



A storage battery equipment will be a necessity, small and port- 

 able, for the substations, but of considerable capacity for the main 

 observatory. Especially should this be the case if laboratory work is 

 undertaken, as this will undoubtedly involve the production of high 

 temperatures which can best be done electrically. In this case also 

 accurate means of measuring high temperatures will be necessary 

 and a variety of laboratory sources of radiation should be available. 



Of course, work would be greatly facilitated by a generous assort- 

 ment of miscellaneous laboratory apparatus, such as small spectro- 

 scopes, telescopes, mirrors, polarizing apparatus, air-pumps, etc., 

 and a lot of laboratory supports and attachments. Finally, as much 

 of a shop equipment as is possible. 



In connection with the spectrobolographic work, I must confess 

 that at present the further detailed study of the infra-red solar lines 

 does not seem to promise very much. Undoubtedly the true solar 

 lines can be separated from those of terrestrial origin and identified 

 to a greater or less extent with emissions of known elements, and 

 this would perhaps be of most value in connection with the question 

 of the persistence of given emissions through long ranges of tem- 

 perature. Again, if the sun's surface were studied in greater detail 

 the infra-red lines might help in the study of motions in the solar 

 atmosphere, but it does not seem likely that they would be more 

 important for that purpose than the lines photographically observable. 

 Of course, it may be found that the infra-red lines behave in some 

 ways quite differently from those of shorter wave length, and hence 

 furnish a valuable tool for solar investigation, but it does not seem 

 to me that the work so far done leads one to expect this. However, 

 you know much better than I what to expect. Again, is it not true 

 that the solar constant work and the separation of true solar lines 

 from those of terrestrial origin are the parts of the work which really 

 demand the high and low mountain stations, while much, if not all, 

 of the other work, on account of its more intimate connection with 

 laboratory experimentation, could better be carried on at a more 

 centrally located observatory; for example, the Yerkes, best of any. 



