THE BELFAST ADDRESS. 181 



Another, of still wider grasp and more radical signifi- 

 cance, is the doctrine of the Conservation of Energy, 

 the ultimate philosophical issues of which are as yet 

 but dimly seen that doctrine which ' binds nature fast 

 in fate ' to an extent not hitherto recognised, exacting 

 from every antecedent its equivalent consequent, from 

 every consequent its equivalent antecedent, and bring- 

 ing 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,* and after- 

 wards with profound insight to organic nature. The 

 vegetable world, though drawing all its nutriment 

 from invisible sources, was proved incompetent to 

 generate anew either matter or force. Its matter is for 

 the most part transmuted gas; its force transformed 

 solar force. The animal world was proved to be equally 

 uncreative, all its motive energies being referred to the 

 combustion of its food. The activity of each animal, 

 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 determined 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. 



* Dr. BerthoUl has shown that Leibnitz had sound views re- 

 garding the conservation of energy in inorganic nature. 



