692 THE NEW SPECTRUM. 



The speaker had been much inde])ted to others for the perfection to 

 which the apparatus, and especiall}^ the galvanometer, had been brought. 

 He was under obligations, particularly to Mr. Abbot, for assistance in 

 many wa3^s, which he had tried to acknowledge in the A'olume; but 

 before closing this most inadequate account of it, he woidd like to 

 draw attention to one feature which was not represented in the spec- 

 trum map before them, although it woidd be found in the book. 



During earl}^ years the impression had been made upon him that 

 there were changes in the spectrum at difierent j^eriods of the year. 

 Some of these changes might be in the sun itself. The major portion 

 of those he was immediatelj^ speaking of, he believed, were rather 

 referable to absorptions in the earth's atmosphere. 



Now these early impressions had been confirmed b}^ 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 alti- 

 tude, and its I'ays to traverse about the same absorbing quantity of 

 the earth's atmosphere), the energy spectrum was distinctly difi'erent 

 in spring, \u summer, in autumn, and in winter. The lateness of the 

 hour prevented him from enlarging on this latter profound!}^ interest- 

 ing subject. He would only briefly point out the direction of these 

 changes, which were not perhaps to ])e called conspicuous, but which 

 seemed to be ver}'^ clearly brought out as certainly existing. 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, with- 

 out 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 begin- 

 ning 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 by means some- 

 what similar to those previsions made day by day by the W^eather 

 Bureau, but in ways inlinitel}^ more far-reaching, and that these might 

 be made from the direct stud}^ 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 ssij that recent 

 studies of others as well as of the writer, strongl}^ point in the direction 

 of some such future power of prediction. 



