3J8 Notices respecting Nciv Books. 



njcntions what Mr. N. had pubHshtd on carpentry, in terms 

 of warm commendation. 



Though only now published, the Essay on the Teeth of 

 Wheels was written several years ago. The author's inten- 

 tions in iliis publication will appear from his short preface, 

 which we shall here transcribe. 



Preface. 



"Led from situation, ;is well as curiosity, to attend very 

 minutely to some parts of practical mechanics, one of the 

 objects, which early attracted the notice of the author of 

 the foUowinjj; short Essay, was the figure of the teeth of 

 wheels. He observed, that, in forming tlicse teeth, work- 

 tiien followed rules for which thcv could assign no satisfac- 

 tory reason: — nor did he then find in books the information 

 he wanted : the subject seemed to him to require a detail 

 •and simplification, wliich no English writer, with whom he 

 was acquainted, had given it. Afterwards, indeed, he found 

 that some French mathematicians had treated it With much 

 attention. But tlicir works, though sufliciently clear to 

 those who have studied mathematics, are too abstract to be 

 of general utility. In the following Essay, therefore, such 

 an elucidation of the subject has been attempted, as might 

 render it plain to the operative mechanic — an object, which 

 will appear the more important the more wc consider the 

 great variety of useful purposes to which wheel-work is ap- 

 plied. 



"De La Hire and Cannis are the two French writers who 

 have treated most extensively this branch of mechanics. 

 From the work of the latter, who has written more accu- 

 rately and more fully, the author has borrowed largely; 

 nor has he scrupled to take from others whatever he found 

 to suit his purpose, and to make the fullest use of the com- 

 ttiunicatlons of his friends. 



<'0f the method followed, it will be sufficient to remark, 

 that the subject naturally suggested these two general divi- 

 sions — First, The principles of the configuration of the teeth 

 cf wheels : — Secondly, The application of these to practice. 



" The first chapter contains the principles. The second, 

 their application, with certain modifications — 1st, to Sptir 



Geer, 



