166 ANNUAL OF SCIENTIFIC DISCOVERY. 



together; a feat which the most experienced analyst would find It 

 almost impossible, even after the most lengthened and careful investi- 

 gation, to accomplish with the older methods. 



In endeaA r oring, says a writer in the Edinburgh Review, to form an 

 idea of the present and future bearings of the science of spectrum 

 analysis as applied to the investigation of terrestrial matter, we must 

 remember that the whole subject is as yet in its earliest infancy ; that 

 the methods of research are scarcely known ; and that speculations 

 as to the results which further experiments will bring forth, are, 

 therefore, for the most part, idle and premature. We may, however, 

 express our opinion that a more intimate knowledge of the nature of 

 the so-called elements, if it is to be attained at all, is to be sought for 

 in the relations which the spectra of these substances present ; and 

 if a " transmutation " of these elementary bodies be effected, as is by 

 no means impossible, it wi?l be effected by help of the new science of 

 spectrum analysis. That we shall thus gradually attain a far more 

 accurate knowledge of the composition of the earth's crust than we 

 now possess, is perfectly certain ; nor is it less certain that, with the 

 progress of the investigation, other new elementary bodies will be 

 added to our already somewhat overgrown chemical family. We 

 anticipate, moreover, important results to the art of medicine from 

 the application of spectrum analysis to mineral waters, as they are 

 termed, noted for their therapeutic qualities. The composition of 

 these waters, their apparently inexhaustible faculty of reproduction, 

 their modes of affecting the human frame in various states of health 

 and disease, are only known as yet empirically. But it is altogether 

 probable that the application of spectral analysis to the elements 

 contained in these springs will bring them within the range of ac- 

 curate medical knowledge, and perhaps extend the resources of 

 medicine itself. 



So long ago as 1815, Fraunhofer made the important observation, 

 that the two bright yellow lines which we now know to be the sodium 

 lines were coincident with, or possessed the same degree of refrangi- 

 bility as two dark lines in the solar spectrum called by Fraunhofer 

 the lines D. A similar coincidence was observed by Sir David Brew- 

 ster, in 1842, between the bright red line of potassium and a dark 

 line in the solar spectrum called Fraunhofer's A. The fact of the 

 coincidence of these lines is easily rendered visible if the solar spec- 

 trum is allowed to fall into the upper half of the field of our tel- 

 escope, whilst the sodium or potassium spectrum occupies the lower 

 half. The bright lines produced by the metal, as fine as the finest 

 spider's web, are then seen to be exact prolongations, as it were, of 

 the corresponding dark solar lines. 



Although the fact of the coincidence of several bright metallic lines 

 with the dark solar lines was well known, yet the exact connection 

 between the two phenomena was not understood until Prof. Kirch- 

 hoff investigated the subject. Nevertheless, before he gave the exact 

 proof of their connection, some few bold minds had foreseen the con- 

 clusions to which these observations must lead, and had predicted the 

 existence of sodium in the sun. 



Wishing to test the accuracy of this frequently asserted coinci- 

 dence of the bright metallic and dark solar lines with his very deli- 



