314 THE POPULAR SCIENCE MONTHLY. 



undertake a subject outside of, though ancillary to, the work with which 

 I am chiefly occupied, a contemplated reply to these criticisms has beer 

 put aside for a while. The article by Mr. Martineau, in the April num- 

 ber of the Contemporary Review, on " The Place of Mind in Nature, and 

 Intuition in Man," while it reminded me of this postponed essay, be- 

 cause containing further criticisms to be met, did not lead to any change 

 of intention. I learn, however, that Mr. Martineau's arguments, which, 

 though not avowedly directed against propositions asserted or implied 

 in " First Principles," tell against them by implication, are supposed by 

 some to be conclusive, and that, in the absence of replies, it will be as- 

 sumed that no replies can be made. It seems desirable, therefore, to 

 notice these arguments at once especially as the essential ones may, I 

 think, be effectually dealt with in comparatively small space. 



The first definite objection which Mr. Martineau raises is, that the 

 hypothesis of general evolution is powerless to account even for the 

 simpler orders of facts in the absence of numerous different substances. 

 He argues that, were matter all of one kind, no such phenomena as 

 chemical changes would be possible, and that, " in order to start the 

 world on its chemical career, you must enlarge its capital, and present 

 it with an outfit of heterogeneous constituents. Try, therefore, the 

 effect of such a gift ; fling into the preexisting caldron the whole list 

 of recognized elementary substances, and give leave to their affinities 

 to work." The intended implication obviously is, that there must exist 

 the separately-created elements before evolution can begin. Here, 

 however, Mr. Martineau makes an assumption which few, if any, chem- 

 ists will commit themselves to, and which many will distinctly deny. 

 There are no " recognized elementary substances," if the expression 

 means substances known to be elementary. What chemists, for conven- 

 ience' sake, call elementary substances, are merely substances which 

 they have thus far failed to decompose ; but, bearing in mind past ex- 

 periences, they do not dare to say that they are absolutely undecom- 

 posable. Water was taken to be an element for more than 2,000 years, 

 and then was proved to be a compound ; and, until Davy brought a 

 galvanic current to bear upon them, the alkalies and the earths were sup- 

 posed to be elements. So little true is it that the " recognized element- 

 ary substances " are supposed to be absolutely elementary, that there 

 has been much speculation among chemists respecting the process of 

 compounding and recompounding by wdiich they have been formed out 

 of some ultimate substance some chemists having supposed the atom 

 hydrogen to be the unit of composition, but others having contended 

 that the atomic weights of so-called elements are not thus interpreta- 

 ble. If I remember rightly, Sir John Herschel was one, among others, 

 who, some five-and-twenty years ago, threw out suggestions respecting 

 the composition of them. What was at that time a suspicion has now 

 become practically a certainty. Spectrum analysis yields results wholly 

 irreconcilable with the assumption that the conventionally-named sim- 



