598 THE POPULAR SCIENCE MONTHLY. 



own to shame, while they are at the same time forming a school of in- 

 vestigators. We do not grudge to Germany all the praise she well 

 deserves, and the influence which the results of German research exer- 

 cise on other nations is likely to urge them to such vigorous and de- 

 termined efforts, that, sooner or later, science and every other pro- 

 gressive influence shall be " great gainers." Meantime, however, Ger- 

 many is doubtless in the ascendant. 



In the year 1845 appeared the first volume, and in 1846 the second, 

 of Humboldt's " Cosmos." As comprising a view of the whole created 

 universe depicted with the most wonderful sympathy, the book is as 

 it were a canon forming a key to every thing that was known of Na- 

 ture at the time. No man was then more suited for such work than 

 was in the highest degree A. von Humboldt. A "Divina Comraedia" 

 of science, the " Cosmos " embraced the whole universe in its two 

 spheres, heaven and earth. Under the leadership of the great searcher 

 of Nature, as Dante once by the hand of Virgil, we climb from the 

 depths of the universe, with its farthest nebulae and double stars, 

 down through the star depths to which belongs our solar system, to 

 the air- and sea-enveloped earth, where form, temperature, and mag- 

 netic condition, are unveiled to us ; then to the wealth of organic life, 

 which, stimulated by the light, unfolds itself on its surface. It is an 

 overwhelming picture of Nature, of surpassing beauty of outline, 

 abounding in grand perspective, with the most careful execution of the 

 smallest detail. 



But we cannot conceal from ourselves that the " Cosmos," pub- 

 lished twenty-five years ago, is in many of its parts now antiquated, 

 not merely because it is wanting in many facts which have since been 

 discovered, but most particularly because Humboldt was ignorant of 

 some highly-important questions which have since taken their place in 

 the foreground of scientific discussion, while our scheme of the uni- 

 verse during the last ten years has been considerably modified by the 

 introduction of new and influential ideas. Any one, who to-day would 

 attempt to recast the " Cosmos," must proceed like the Italian archi- 

 tect who took the pillars and blocks of the broken temples of antiquity, 

 added new ones, and rebuilt the whole after a new plan. 



There are three discoveries which, during the last quarter of a cen- 

 tury, have entirely changed the position of natural science : the me- 

 chanical equivalent of heat, spectrum analysis, and the Darwinian 

 theories. 



Since, in the year 1842, an unknown physician in a Swabian coun- 

 try-town, Dr. Mayer, of Heilbronn, pointed out that a hammer 424 

 kilogrammes in weight, which falls from the height of a metre on an 

 anvil, raises the heat of the latter by one degree centigrade, and that 

 by this process of bringing a falling motion to a stand-still it is con- 

 verted into a fixed quantity of heat since then has science gained a 

 new conception of the conditions of matter and of the powers of Na- 



