S6 Blake on the Teeth of Cog- Wheels. 



principles, or in other words, that he begin with practice 

 and end in theory. This is the very order of nature, for 

 our first notices of things, are simple, and practical, and we 

 then proceed to enquire into their foundation, and the causes 

 of their phenomena. 



The second Vol. of our author's very extensive work on 

 mechanics is occupied altogether with what may be denom- 

 inated practical mechamcs ; this not only applies to prac- 

 tice, some of the important theories of the first volume, but 

 goes very extensively into the description by language and 

 drawing, of almost every machine, engine, or mechanical 

 work of ingenuity, which as yet, has resulted from the exer- 

 ercise of the human faculties in this branch of science. 

 This portion of the work, will, we believe, be by far the 

 Hiost acceptable to the real mechanician, as that of the first 

 volume can only be so for the most part, to profound math- 

 ematicians, or men of rare genius, and acquirements. 



We will conclude our remarks, which we fear, have al- 

 leady been extended too far into details, with a concise 

 ©pinion of the merit and importance, which may justly be 

 attributed to this work as a whole, embracing a mass of sci- 

 entific materials. In this respect, we consider it as the 

 most valuable and comprehensive system of mechanics in 

 the English language. Though the theoretical part has 

 been studiously rendered abstruse and difficult to beginners, 

 by the overweaning attachment of the author for analytics, 

 and sometimes for metaphysical discussions, there is besides 

 an abundant supply of useful theory, illustrated in a plain 

 elementary style and method. No reader can be at a loss 

 in selecting such portions of the book, as are within the 

 scope of his genius and capacity. But if any can go 

 farther, and make himself master of the whole of this 

 work, he will have little else to search for, to obtain all the 

 discoveries, and improvements, which have been made in 

 this science. 



Art. XI. — On the form of the teeth of Cog- Wheels ; by 

 Eli W. Blake, A. M. New-Haven. 



It is very important in most kinds of Wheel Work that 

 such a form should be given to the acting faces of the teeth 



