i 3 8 



THE POPULAR SCIENCE MONTHLY. 



mile in average actual thickness, of which 

 probably one tenth consists of calcareous 

 matter. In seeking the origin of this calcare- 

 ous matter, it is assumed that the primitive 

 rocks of the original crust were of the nature 

 of granitic or basaltic rocks. By disintegra- 

 tion of such rocks, calcareous and other sedi- 

 mentary deposits have been formed. The 

 amount of lime-salts in waters which drain 

 districts made up of granites and basalts is on 

 an average about 3 - 75 parts in 100,000 parts 

 of water. It is further assumed that the 

 exposed areas of igneous rocks, taking an 

 average throughout all geological time, will 

 bear to the exposures of sedimentary rocks 

 a ratio of about one to nine. From these 

 and other data Mr. Reade concludes that 

 the elimination of the sedimentary strata 

 must have occupied at least six hundred 

 million years. This would be the minimum 

 age of the world. The author infers that 

 the formation of the Laurentian, Cambrian, 

 and Silurian strata must have occupied 

 about two hundred million years ; the Old 

 Red Sandstone, the Carboniferous, and the 

 Poikilitic systems another two hundred 

 million ; and all the other strata the re- 

 maining two hundred million. 



Professor Clarke on Lockyer's Research- 

 es. Professor F. W. Clarke, of Cincinnati, 

 sends a letter to "Science News " in relation 

 to the recent views of Mr. Lockyer on the 

 compound nature of the chemical elements. 

 Professor Clarke was himself early in that 

 field, and published a very suggestive article 

 in "The Popular Science Monthly" of Jan- 

 uary, 1873, on " Evolution and the Spectro- 

 scope," in which he announced on spectro- 

 scopic grounds the hypothesis that the evo- 

 lution of planets from nebula had been 

 accompanied by an evolution of complex 

 from simple forms of matter. The idea 

 was based upon the gradation in chemical 

 complexity of the celestial spectra. About 

 eight months later Mr. Lockyer put forth es- 

 sentially the same views, resting them upon 

 exactly the same evidence. Professor Clarke 

 then goes over the ground recently taken 

 by Lockyer, and recognizes that he has de- 

 cidedly advanced the inquiry from a theo- 

 retical point of view. He traces the new 

 lines of evidence, and considers that absolute 

 demonstration may perhaps be attainable 



only by an actual decomposition of the ele- 

 ments in the laboratory ; but a probability 

 so strong as to command universal accept- 

 ance may be otherwise established. Mr. Lock- 

 yer has done much toward establishing this 

 probability, and it is to be hoped that he 

 will successfully continue his labors in the 

 same direction. Meanwhile, chemists must 

 seek new evidence from other sources, un- 

 til, one way or another, the vexed question 

 shall be laid definitely at rest. 



The Distinctions between Man and Ani- 

 mals. In a brief and sprightly, if not very 

 profound article, a writer in the " Monthly 

 Journal of Science " examines the validity 

 of one of the principal distinctions which 

 have been drawn between man and animals, 

 namely, the supposed fact that while men 

 progress as individuals, as communities, 

 and as a species, animals stand stock-still, 

 each succeeding generation attaining just 

 the development of its predecessor and no- 

 thing more. The author, on the contrary, 

 maintains that the individual man does not 

 make progress from the cradle to the grave, 

 but that, from the middle of life, and often 

 indeed from an earlier date, he is a mere 

 bundle of habits and prejudices : no further 

 mental growth is possible, however long he 

 may happen to survive. To a man, then, 

 brutes exhibit no well-marked contrast, but 

 a decided similarity : in the earlier part of 

 life they are, like ourselves, capable of prog- 

 ress ; but later their faculties are blunted, 

 and, like man, they become stationary ; as 

 far, therefore, as individual progress is con- 

 cerned, man and beast differ only in degree. 

 There is also among mankind a national or 

 tribal progress distinct from that of the in- 

 dividual and that of the species, but, like 

 them, not unlimited in extent and duration. 

 Nations decay, and the cause of this decay 

 is to be sought in the decline of that which 

 in a nation corresponds to vitality in the 

 individual the " tribal instinct." Among 

 those animal species which live in organized 

 communities or nations the very same phe- 

 nomenon occurs, and every ant-hill might 

 have its Gibbon. The author here cites the 

 observations of Berthelot, already quoted 

 in the " Monthly" (current volume, p. 248.) 

 It remains to consider the real or fancied 

 superiority of every generation of mankind 



