Notices respecting New. Books, 31t> 



Geer, under which are coinprehcndt'd, the tvheel and trun- 

 dle; ihe ic/icel and pinion; the internal pinion, and the ruck 

 and pinion — and, adiv, to Bevd Geer. 



" A third chapter is added, which contains a manner of 

 forming spur wheels, upon principles sonieuhai ditferent 

 irom those considered in the preceding chapter. 



" fn the following pages no pretensions are made either 

 to invention or profound investigation. The writer has 

 studied perspicuity alone, and will have completciy attained 

 his object, if he has only been fortunate enouuh to give 

 such a view of the various kinds of teeth, as will enable the 

 artist to form sonic judgment of their respective merits, and 

 to execute any of thenj with accuracv and ease. For this 

 purpose it has been his aini to divest every part of the subject 

 of obscurity, and to accommodate it to those who possess 

 not the advantages of a mathematical education. Rut lie is 

 far from saying that they will not find some difticulties, 

 particularly in the first chapter; nor will they, perhaps, 

 fully understand the truths it contains, till they see their 

 relation to practice pointed out in the second. He found, 

 that without becoming exceedingly prolix, there was no 

 avoiding the use of some mathematical terms ; but of these 

 he has gi\-en dcfinilions, either as the terms themselves oc- 

 cur, or at the conclusion of the Essay*." 



The Essay is followed by a letter containing some scien- 

 tific and useful observations on the friction of the teeth of 

 wheels, by Dr. Young, formerly professor of natural phi- 

 losophy at the Royal Institution f. There follows a Post- 

 script and Appendix. The appendix contains ^' A practical 

 inquiry rcspccfbig the Strtni^lh and Durability of the Tveih of 

 IVheels used in Allllivorh." This subject we consider of 

 much importance, but it is involved in considerable difficulty. 



" I am aware," says Mr. 13. " that owing to a great va- 

 riety of circumstances, this subject is involved in much dif- 

 ficulty, and that it is no easy task to form any general rule 



• Tliis preface was written several years btfore the translation of C.imus 

 wa«pul>li;>hcd. 

 ' • I This gentleman's Lectures on N.t tal Philcs'jphy, lately puljlished, we 

 beg leave to icconsniciid to thi attention of our reader*. 



with 



