241 



energy, that has been expended in hmlesqueing physical energy 

 had been devoted to obtaining a fuller comprehension of the 

 subject, the cause of truth might not have been more efficiently 

 promoted. 



59. Two further points only of Dr. McCann^s paper will here 

 be remarked upon. The quotation (§ 20) from Mr. Spencer's 

 First Principles is an elaborate but, to my mind, confused 

 statement of the perfectly distinct and definite ideas of absolute 

 and relative motion. He writes — " A body impelled by the 

 hand is clearly perceived to move, and to move in a definite 

 direction,^' i. e., relatively to the perceiver and surrounding 

 objects, beyond which perception cannot extend, for the per- 

 ception must obviously be the same whether the observer were 

 absolutely at rest in space, or whether he and the observed 

 body partake alike of the earth^s rotation on its axis and 

 revolution round tlie sun, and the progression, if any, of the 

 entire solar system in space, and any other motion or motions, 

 conceivable or inconceivable — and that is the whole question. 



60. In reference to Mr. Spencer's gratuitous assumption (§ 1) 

 that the various forms of physical and mental energy are recip- 

 rocally convertible, he writes (§ 41) : — "That such is a fact 

 may be assumed but can never be proved till some instrument 

 be constructed capable of measuring the velocity of thought ; '' 

 evidently not being aware that such an instrument had been 

 constructed some years since, and satisfactory experiments made 

 by Drs. Hirsch, De Jaager, and Bonders ; * but they aflPord no 

 confirmation of Mr. Spencer's assumptions, beyond the fact 

 that time is an element in mental operations ; but until the 

 precise train of physical changes in the brain and nerves which 

 accompanies perception and thought can be fully ascertained 

 (an amount of knowledge obviously beyond the reach of man), 

 the hypothesis in question must be held to be insusceptible 

 of proof. 



61. It may, in conclusion, be remarked with much regret that 

 the principle of the conservation of energy has by some been 

 misapplied to questions far beyond its legitimate scope, in a 

 fruitless endeavour to supersede the necessity of an omniscient 

 Creator. To the mind of the writer, and, it is earnestly hoped, 

 to that of most of his hearers and readers, the indisputable esta- 

 blishment of this principle conveys only a more exalted idea of 

 that infinite wisdom by which the perpetually recurring trans- 

 formations and interchanges, not only of the materials, but also 

 of the powers, of Nature are rendered subservient to predeter- 

 mined laws, which govern the comfort and welfare of all created 



Elements of Natural Philosophij, sixth edition, p. 568. 



