6 PRESIDENTIAL ADDRESS BY 



same manner as exposure to sunlight. It is found also tliat the electric current will make 

 carbon and hydrogen comliine, and, again, the same electric current Avill undo the union of 

 substances chemically united, as in the deposition of metals from their solutions or the 

 dissociation of nitrogen and hydrogen in ammonia. 



It has lately been showu that simple mechanical friction will effect a similar dissociation. 

 Thus, silver chloride is reduced to the metallic state by simply rubbing in a mortar. It is 

 also known that not only is chemical union determined by light, but chemical dissociation 

 is also brought about by that agency. Thus, carbon dioxide is decomposed by light in the 

 tissues of plants. Here it may be said that the living tissue, assisted by light, enables the 

 cells to bring about this change, but in the case of silver and gold and iilatinum salts, light 

 alone is able to bring about the dissociation. 



In all these cases of chemical union or separation by the agency of heat or light, or 

 electricity or mechanical action, all that has been done is to increase the molecular vibra- 

 tions, at one moment by slight increase to bring about union, at another Ijy still further 

 increase to determine separation. 



Hence it is observed that molecular vibrations produced by mechanical action or friction 

 will determine chemical union or separation ; molecular vibrations produced by mechanical 

 means, by heat, by light or by electricity will determine either the union or separation of 

 chemical compounds. And it has been found that definite amounts of heat, that is, 

 molecular vibration, are produced or absorlied by the uniiui or separati(Ui of definite amount 

 of different kinds of matter. 



Again, it is observed that if the mechanical, light or electrical vibrations are arrested, 

 they are converted into heat, and contra, heat vilu'ations may be increased to produce light 

 and electricity. Thus all these agencies may be looked upon as difterent manifestations of 

 molecular vibrations. There are other points of similarity between them showing their 

 common origin, their capability of reflection and refraction. 



To o-o a step further, it is well known that seeds of plants or spores are made to grow 

 bv the agency of heat in presence of moisture, and I^ixon has shown that moisture is neces- 

 sary for chemical union as well as heat. He has shown that perfectly dry oxygen and 

 hydrogen do not explode when fire is brought to them, unless moisture in the form of 

 vapour is also present. 



Eggs can be hatched, in other words, made to grow by increasing the heat, that is, 

 the molecular vil)ratious to which they are subjected. 



So that both animal and vegetable development is due to increase of heat ; that is, to 

 increase of molecular vibrations. Again, life is arrested by increase of heat, and may be 

 kept dormant l>y either too high or too low a temperature. Thus fermentation is stopped 

 by an elevation of temperature above 85 ' or by a decrease of temperature below 70 , and, 

 further, it is found that all life is arrested by too high or too low a temperature. In other 

 words, too much or too little molecular vibrations will arrest both animal and vegetable 

 o-rowth. It has lately been shown that a current of electricity will hasten the germination 



of seeds. 



Many solid substances, neither animal nor vegetable, dissolve in water, and if the 

 process of solution be examined it will be found that the molecules of the liquid solvent 

 bombard the molecules of the solid until disintegration takes place ; that heat will aid in 

 this process of solutiou uji to a certain point ; and if the solution be allowed to give up its 



