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I do not altogether agree with Mr. Kitchin in one or two 

 points. I think that the theory which implies practice must not 

 be confounded with hypothesis ; it is, in fact, much the same as 

 general knowledge or science. Mr. Kitchin says that the bringing 

 to bear upon everyday life an accumulated knowledge of facts is 

 not the application of theory to practice. It is not the application 

 of hypothesis to practice ; it is the application of knowledge to 

 practical purposes ; and whenever knowledge is for the first time 

 applied to the useful purposes of life, there is an element of 

 uncertainty, not necessarily in the knowledge itself, but as to 

 whether the desired result will follow its application. It is assumed 

 that the desired result will follow its application. Before the 

 uncertainty is removed the knowledge, coupled with the idea of 

 making a practical use of it, has received the name of theory ; 

 after the uncertainty has been removed it is called experience, and 

 is then utilised for practice. 



I differ from Mr. Kitchin in reference to what he says about 

 the atomic theory. It is not supported by facts : it is a mere 

 hypothesis devised by Dalton to explain facts, and it is quite 

 within the bounds of possibility that it may hereafter be supplanted 

 by some other hypothesis which explains the facts better. . I hardly 

 think that the practice of chemistry is based upon the atomic 

 theory as Mr. Kitchin has enunciated it, but rather upon the laws 

 the theory is assumed to account for. These laws are four in 

 number, and are called the laws of chemical combination. It 

 would perhaps be well to explain briefly at least one of them. I 

 will take that one called the law of multiple proportion. It asserts 

 that, when one substance combines with another in several pro- 

 portions, the higher are multiples of the lowest. Thus 10,000 

 ounces of nitrous oxide contain 6,364 ounces of nitrogen, and 

 3,636 ounces of oxygen; 10,000 ounces of nitric oxide contain 

 4,667 ounces of nitrogen and 5,333 ounces of oxygen. By reducing 

 these numbers, we find that, in the former compound, the propor- 

 tions of nitrogen and oxygen are 28 and 16 ; and in the latter 

 the proportions are 28 and twice 16; and so with three other 

 compounds of nitrogen and oxygen, the proportions are 28 and 



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