244 TRANSACTIONS OF THE [mAY 17, 



prize of the Frencli Academy of Sciences last January, and the 

 still more accurate and important map photographed by Pro- 

 fessor Iiowland, by means of his wonderful diffraction gratings, 

 and now in course of publication. Nor would it be just either 

 to omit the earlier and less accurate maps of Fievez and 

 Vogel, which, when published, were as far in advance of anything 

 before them as they are behind the new ones; nor the maps just 

 made by Professor Smyth, of Edinburgh. 



It was in connection with tiie construction of such a map by 

 Mr. Lockyer, that he was led to his theory of the compound 

 nature of the so-called chemical elements, partly as a result of 

 his comparisons of the spectra of different substances with the 

 solar spectrum, and partly in consequence of considerations 

 drawn from certain phenomena observed in the solar and stellar 

 spectra themselves. His first })aper on the subject was read late 

 in 1878. This " working hypothesis, '' as its author calls it, has 

 met with much discussion, favorable and unfavorable. Ituncpies- 

 tionably removes many diflHculties, and explains many puzzling 

 phenomena; at the same time there are very serious objections 

 to it, and some of the arguments upon which Mr. Lockyer origi- 

 nally laid much stress have turned out unsound. For instance, 

 he made a great point of the fact that, after all precautions are 

 taken to remove impurities, several elementary substances show 

 in their spectra common lines — "basic lines" he called them — 

 indicating, as he thought, a common component. He found in 

 the solar spectrum about seventy of these "basic lines." Now, 

 under tlie high dispersion of our newer spectroscopes, these lines, 

 which were single to his instruments, almost without exception 

 dissolve into pairs and triplets, and withdraw their support from 

 his theory. 



I supj)ose that at present the weight of scientific opinion is 

 against him; but for one I do not believe his battle is lost. In 

 view of the law of Dulong and Petit, which establishes a relation 

 between the atomic weight: and specific heat of bodies, it seems 

 to be pretty certain that hydrogen cannot be the elementary " ur- 

 stoff" out of which all other elements are made by building up, 

 as lie at first seemed disposed to maintain; this element stands 

 apparently on no different footing from the rest. But I see no 

 reason why the elements, as we know them, may not consti- 

 tute one class of bodies by themselves, all built up out of some 

 as yet more elemental substance or substances. The " j)eriodic 

 law " of Mendeljeff suggests such a relation. And our received 

 theories so stumble, hesitate, and falter in their account of many 

 of the simplest phenomena of the solar and stellar atmos[)heres, 

 that a strong presumption still remains in favor of the new 



