470 THE POPULAR SCIENCE MONTHLY. 



would lead to an alarming multiplication of elementary bodies, in- 

 creasing our present confusion to an indefinite extent. If every pos- 

 sible wave-length of light represented a special element, the num- 

 ber of elements would be infinite. Clearly, then, this speculation, 

 although frequently suggested, has very little to recommend it, and 

 need not be entertained. Still, the fact of varying complexity among 

 the elementary spectra remains to be accounted for. It certainly sug- 

 gests a corresponding difference of complexity among the elements 

 themselves, but of what nature ? This question can hardly be an- 

 swered directly, although it admits of interesting discussion, for 

 which, unfortunately, we have little space to spare. Suffice it to say 

 that spectroscopic phenomena are quite in harmony with the idea 

 that all matter is at bottom one, our supposed atoms being really vari- 

 ous aggregations of the same fundamental unit. It is approximately 

 true that the simpler spectra are furnished by the elements of low 

 atomic weight, while the multitudes of lines come from the heavier 

 atoms. There are prominent exceptions to this rule, still it affords 

 some support to our central idea. 



But the spectroscope makes its most emphatic suggestions in favor 

 of the unity of matter when it is applied to the study of the heavenly 

 bodies. This subject I discussed in The Popular Science Monthly 

 for January, 1873, and some months later Lockyer gave it prominence 

 in England, his paper calling forth a good deal of comment. There- 

 fore, only a brief resnyne of my original suggestions is desirable now. 



Everybody knows that the nebular hypothesis, as it is to-day, 

 draws its strongest support from spectroscopic facts. There shine 

 the nebulae in the heavens, and the spectroscope tells us what tliey 

 really are, namely, vast clouds of incandescent gas, mainly, if not 

 entirely, hydrogen and nitrogen. If we attempt to trace the chain 

 of evolution through which our planet is supposed to have grown, we 

 shall find the sky is full of intermediate forms. The nebuloe them- 

 selves appear to be in various stages of development ; the fixed stars 

 or suns differ widely in chemical constitution and in temperature ; our 

 earth is most complex of all. There are no " missing links " such as 

 the zoologist longs to discover when he tries to explain the origin of 

 species. First, we have a nebula containing little more than hydro- 

 gen ; then a very hot star with calcium, magnesium, and one or two 

 other metals added ; next comes a cooler sun in which free hydrogen 

 is missing, but whose chemical complexity is much increased ; at last 

 we reach the true planets with their multitudes of material forms. 

 Could there well be a more straightforward story ? Could the unity 

 of creation receive a much more ringing emphasis ? We see the evo- 

 lution of planets from ncbula3 still going on, and parallel with it an 

 evolution of higher from lower kinds of matter. 



Just here, perhaps, is the key to the whole subject. If the ele- 

 ments are all in essence one, how could their many forms originate 



