Vlll PREFACE. 



instead of helps. "We can now see that when the true chemistry 

 of combustion was once reached, the notion of phlogiston was of 

 no further use, and if retained could only produce confusion and 

 prevent the reception of correct ideas. So with caloric, and those 

 false conceptions of the materiality of forces, which it implies : not 

 only are they errors, hut the ideas they involve are radically in- 

 compatible with the higher truths to which science has advanced ; 

 so that while the errors are retained the truths cannot be received. 



Nor will it answer merely to mention the new views while 

 adopting the old, on the plea that the facts are the same in both 

 cases. The facts are very far from being the same in both cases. It 

 is precisely because the old ideas are out of harmony with the facts, 

 and can no longer correctly explain and express them, that new ideas 

 are sought. Was not phlogiston abandoned because it no longer 

 agreed with the facts ? So with the conception of the materiality 

 of the forces ; it contradicts the facts, and therefore, for scientific 

 purposes, can no longer represent them. In the workshop it may 

 perhaps be very well to magnify facts, and depreciate their theoreti- 

 cal explanations, but not in the school-room ; the business is here not 

 working, but thinking. It is the aim of art to use facts, but of sci- 

 ence to understand them. And it is simply because science goes 

 beyond the fact to its explanation, and is ever striving after the 

 highest truth, that it is fitted to discipline the thinking and reason- 

 ing faculties, and therefore has imperative educational claims. 



In therefore bringing forward these able and authoritative ex- 

 positions in a form readily accessible to teachers, I trust I am not 

 only doing them a helpful service, but that they will be led to re- 

 quire of the preparers of school-books a more conscientious per- 

 formance of their tasks, and that the interests of sound education 

 will be thereby promoted. 



NBW YOBK, Oct. 1, 1864. 



