S. P. Langley — New Spectrum. 413 



tried to acknowledge in the volume ; but before closing this 

 most inadequate account of it, he would like to draw attention 

 to one feature which was not represented in the spectrum map 

 before them, although it would be found in the book. ■ 



During early years the impression had been made upon him 

 that there were changes in the spectrum at different periods of 

 the year. Some of these changes might be in the sun itself ; 

 the major portion of those he was immediately speaking of, he 

 believed, were rather referable to absorptions in the earth's 

 atmosphere. 



Now these early impressions had been confirmed by the 

 work of the observatory in recent years, and charts given in 

 the volume would show that the sun, (being always supposed 

 to be at about the same altitude, and its rays to traverse about 

 the same absorbing quantity of the earth's atmosphere,) the 

 energy spectrum was distinctly different in spring, in summer, 

 in autumn, and in winter. The lateness of the hour prevented 

 him from enlarging on this latter profoundly interesting sub- 

 ject. He would only briefly point out the direction of these 

 changes, which were not perhaps to be called conspicuous, but 

 which seemed to be very clearly brought out as certainly exist- 

 ing. With regard to them he would only observe, what all 

 would probably agree to, that while it has long been known 

 that all life upon the earth — without exception — is maintained 

 by the sun, it is only recently that we seem to be coming by 

 various paths, and among them by steps such as these, to look 

 forward to the possibility of a knowledge which has yet been 

 hidden to us, of the way in which the sun maintains it. We 

 were hardly beginning to see yet how this could be done, but 

 we were beginning to see that it might later be known, and to 

 see how the seasons, which wrote their coming upon the records 

 of the spectrum, might in the future have their effects upon 

 the crops, prevised in ways somewhat similar to those previsions 

 made day by day by the Weather Bureau, but in ways infinitely 

 more far-reaching; and that these might be made from the 

 direct study of the sun. 



We are yet, it is true, far from able to prophesy as to coming 

 years of plenty and of famine, but it is hardly too much to say 

 that recent studies of others as well as of the writer strongly 

 point in the direction of some such future power of prediction. 



