120 Mr. M. Donovan on the supposed Identity of the Agent 



electro-magnetic, magneto-electric, and thermo-electric pheno- 

 mena, depends on the ratio, or variable energy, or mode of asso- 

 ciation of the constituent elements, or on the influence of other 

 modifications which, under different circumstances, they are 

 capable of exerting on each other; in one word, that these 

 various classes of phscnomena are caused by different agents ; — 

 these agents as much differing from each other as hundreds ol 

 chemical compounds, which, consisting of the same elements, 

 are so combined and grouped as to constitute and be recognised 

 as independent forms of existence, requiring different names. 

 This modifying influence is probably of the same character as 

 that which the forces of nature exercise on each other on the 

 great scale of creation, controlling, antagonising, and regulating 

 each others' effects ; thus producing the diversified phenomena 

 of the universe, but rarely acting independently. It is by op- 

 posing forces that the earth is maintained in its orbit ; by the 

 interposition of a third force its unity of motion and integrity of 

 substance are preserved. It is by the antagonism of an attract- 

 ive and repulsive power that hardness, softness, liquidity, and 

 fluidity exist ; but for this antagonism the materials of creation 

 would be bound in perpetual rigidity, or attenuated throughout 

 space; neither animal nor vegetable could exist; there could 

 not be either ah- or water. Were it not for the control which 

 the various energies of nature exercise over each other, new forms 

 of things would be produced and destroyed in rapid succession ; 

 change would be perpetual ; nothing would be permanent. It 

 would be easy but useless to multiply examples, since a cursory 

 view of creation will prove that the Almighty rarely regulates 

 the course of natural events by the operation of insulated forces ; 

 there is scarcely a physical phenomenon in which it is not pos- 

 sible to detect the operation of several ; and thus, by combina- 

 tion of elementary causes, a vast variety of effects is produced. 



If it be true that complication of matter and of forces is the 

 method of nature, can we without risk of error single out that 

 most remarkable of her agents, electricity, and affirm that it 

 presents itself to our senses in a state different from that in 

 which all other objects occur, — in an undisguised, uncompounded 

 form ; and that it produces its wonderful, diversified, and im- 

 portant functions in virtue of one single or homogeneous element? 



The opinions here promulgated differ widely from those which 

 are now almost universally maintained by philosophers. By a 

 kind of tacit consent, it has been commonly assumed that the 

 calorific, luminous, dynamic, magnetic, chemical, and physiolo- 

 gical properties of the electric fluid are exercised by it as an 

 uncompounded element; of a constitution invariable and iden- 

 tical under every aspect, unless in the two great varieties of the 



