THE AVAILABLE ENERGY OF NATURE. 87 



ferent circumstances will explain this question. Firstly, meteoric 

 stones are always rare and costly objects, which are not easily sacri- 

 ficed by their possessors, so that hitherto but very few of them have 

 been broken up in order to obtain laminae suitable for microscopic 

 investigation. Then, again, the latter have only been manufactured in 

 limited numbers, so that the probability of discovering a favorable 

 object in them could consequently be but very small. Dr. Hahn, how- 

 ever, has made extraordinary sacrifices, both in time and money, to 

 obtain his specimens, of which he now possesses no less than six hun- 

 dred. It must also be mentioned that hitherto the investigations of a 

 few specimens have been made with a magnifying-glass only, and but 

 seldom with powerful microscopes, such as Dr. Hahn employs. 



Besides thus affording positive proof of the fact that other worlds 

 are or have been inhabited by organic beings, this important discovery 

 has also solved another interesting problem, which has long perplexed 

 the scientific world. By the newest theory of the celebrated astrono- 

 mer Schiaparelli regarding meteorites, the latter were supposed to ema- 

 nate from incandescent comets and their tails. Now all the petrified 

 organisms discovered by Dr. Hahn have been proved to belong to the 

 subaqueous classes of animals, and indeed have lived in water which 

 never froze entirely, and for which we would certainly have to look in 

 vain in comets, which are now generally admitted to be in a state of 

 active combustion. 



This affords but another proof of the transcendent importance of 

 this new and great discovery, the general results of which we have 

 now placed before the readers of this journal. 







THE AVAILABLE ENERGY OF NATURE * 



Br Sib WILLIAM THOMSON. 



DURING the fifty years' life of the British Association, the ad- 

 vancement of science, for which it has lived and worked so well, 

 has not been more marked in any department than in one which belongs 

 very decidedly to the Mathematical and Physical Section the science 

 of energy. The very name energy, though first used in its present 

 sense by Dr. Thomas Young about the beginning of this century, has 

 only come into use practically after the doctrine which defines it had, 



grains) in Sweden. The specimens forming this collection have been brought together 

 from all parts of the world, and belong to meteoric falls during several centuries. The 

 first specimen in the catalogue fell on the 7th of November, 1492, in Alsace, and the last 

 on the 12th of February, 1875, in Iowa. 



* Opening address before Section A, at the York Meeting of the British Association 

 for the Advancement of Science. 



