PREFACE. Vll 



briefly noticed in the introductory observations too briefly, I fear, 

 to be satisfactory. Those, however, who desire to pursue still 

 further this branch of the inquiry the correlation of the vital, 

 mental, and social forces are referred to the last edition of Car- 

 penter's " Principles of Human Physiology ; " Morell's " Outlines 

 of Mental Philosophy ; " Laycock's " Correlations of Consciousness 

 and Organization ; " Sir J. K. Shuttle worth's address before the 

 Social Science Congress of 1860, on the "Correlation of the Moral 

 and Physical Forces;" Hinton's "Life in Mature," and "First 

 Principles " of Herbert Spencer's new system of Philosophy. The 

 first and last of these works are the only ones, it is believed, that 

 have appeared in an American form, and the last is much the 

 ablest of all ; I was chiefly indebted to it in preparing the latter 

 part of the introduction. The biographical notices, brief and im- 

 perfect as they are, it is hoped may enhance the reader's interest 

 in the volume. 



I have been specially incited to procure the publication of a 

 work of this kind, by the same motive that has impelled me to 

 write upon the subject elsewhere ; a conviction of our educational 

 needs in this direction. The treatment of a vast subject like this 

 in ordinary school text-books, is at best quite too limited for the 

 requirements of the active-minded teacher ; to such, a volume like 

 the present may prove invaluable. 



But a more serious difficulty is that, until compelled by the de- 

 mands of intelligent teachers, the compilers of school-books will 

 pass new views entirely by, or ^ive them a mere hasty and careless 

 notice, while continuing to inculcate the old erroneous doctrines. 

 And thus it is that from inveterate habit, or intellectual sluggish- 

 ness, or a shrewd calculation of the indifference of teachers, out- 

 worn and effete ideas continue to drag through school-books for 

 half a century after they have been exploded in the world of liv- 

 ing science. He who continues to teach the hypothesis of caloric, 

 falsifies the present truth of science as absolutely as he would do 

 in teaching the hypothesis of phlogiston ; in fact, the reasons of- 

 fered for persisting in the erroneous notions of the materiality of 

 heat convenience of teaching, unsettledness of the new vocabu- 

 lary, &c., are precisely those that were offered for clinging to phlo- 

 giston, and rejecting the Lavoiserian chemistry of combustion. 

 Both conceptions have no doubt been of service, but both were 

 transitional, and having done their work they become hindrances 



