CHAPTER I 



GENERAL PRINCIPLES. 



THERE is scarcely anything of more frequent oc- 

 currence than the transition from an incorrect 

 mode of expression to a popular error ; we see instances 

 of this daily occurring. No doubt the incorrect mode 

 of expression usually arises, in the first instance, either 

 from confusion of ideas or false appreciation of facts, or 

 both taken together ; but when once brought into cur- 

 rency, it is frequently accepted not only as a fitting 

 designation, but actually as a true explanation of the 

 nature or mode of operation of the thing designated, 

 and thus grows into what is called a popular error. 



It is more especially in matters connected with me- 

 chanical contrivances that we observe this to take place, 

 and the reason is very obvious. Such modes of expres- 

 sion originate with what are called practical men, who, 

 seldom having leisure or scientific education sufficient 

 to enable them to construct at once correct definitions, 

 commonly judge by the eye or the touch, and translate 

 the evidence of one of these senses into a name. It is 

 in this way that the peculiar languages of handicrafts 

 usually grow up, and the apprenticeship to these con- 

 sists to a great extent in the acquisition of the proper 

 application of such technical terms ; so that, in fact, 

 this sort of language becomes the means of keeping 



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