THE BELFAST ADDRESS 193 



fate, 1 ' to an extent not hitherto recognized, exacting from 

 every antecedent its equivalent consequent, from every 

 consequent its equivalent antecedent, and bringing vital 

 as well as physical phenomena under the dominion of 

 that law of causal connection which, so far as the human 

 understanding has yet pierced, asserts itself everywhere 

 in nature. Long in advance of all definite experiment 

 upon the subject, the constancy and indestructibility of 

 matter had been affirmed; and all subsequent experience 

 justified the affirmation. Mayer extended the attribute of 

 indestructibility to energy, applying it in the first instance 

 to inorganic, 1 and afterward with profound insight to or- 

 ganic nature. The vegetable world, though drawing all 

 its nutriment from invisible sources, was proved incom- 

 petent to generate anew either matter or force. Its mat- 

 ter is for the most part transmuted gas; its force trans- 

 formed solar force. The animal world has proved to be 

 equally uncreative, all its motive energies being referred 

 to the combustion of its food. The activity of each ani- 

 mal, as a whole, was proved to be the transferred activity 

 of its molecules. The muscles were shown to be stores of 

 mechanical energy, potential until unlocked by the nerves, 

 and then resulting in muscular contractions. The speed 

 at which messages fly to and fro along the nerves was de- 

 termined by Helmholtz, and found to be, not, as had been 

 previously supposed, equal to that of light or electricity, 

 but less than the speed of sound less even than that of 

 an eagle. 



This was the work of the physicist: then came the 



1 Dr. Berthold has shown that Leibnitz had sound views regarding the 

 conservation of energy in inorganic nature. 



SCIENCE VI 9 



