VI INTRODUCTION. 



heads, where the names of the respective writers, from whom 

 the extracts have been made, are usually inserted ; and par- 

 ticular care has been taken throughout to admit nothing of a 

 practical nature w r hich has not been sanctioned by unexcep- 

 tionable authorities : at all events, since, in every case which 

 admits not of rigid demonstration, the authority has been most 

 scrupulously quoted, the intelligent reader will at once be able 

 to judge what degree of confidence it is entitled to. 



The small Tables of Logarithms will probably be considered 

 a valuable addition : by the help of these, any one, having the 

 proper data, may exhibit arithmetically such formulae as require 

 a logarithmic computation with sufficient accuracy for all tem- 

 porary purposes. 



Some subjects, which, from their practical utility, might seem 

 to claim a place in this Synopsis, have, in cases where long 

 verbal descriptions or an expensive apparatus of plates were 

 necessary for their illustration, been purposely omitted; it 

 having been a leading object in the compilation to confine the 

 volume within such limits as might render it conveniently 

 portable. Other omissions doubtless there are, which may 

 have proceeded from inadvertence, or a want of judgment in 

 the selection ; but these last will not, it is hoped, be found 

 very considerable, either in point of number or importance. 



To typographical accuracy every possible attention has been 

 paid ; without that, a book of this kind would be worse than 

 useless. 



