PREFACE. IX 



upon which he may require elementary knowledge and the 

 assistance of computations may have escaped the vigilance 

 of the author. 



When a friend first suggested to the author the design of 

 such a work, the latter had no adequate conception of the 

 labor involved in such an undertaking. Although many of 

 the tables were supplied or compiled from other authors, yet 

 the labor involved in those he himself calculated and ar- 

 ranged was prodigious. Besides, the composition or type- 

 setting of the matter was of the most tedious, difficult, and 

 expensive kind, so that the volume of matter included within 

 the covers would seem to bear no just proportion to the price 

 the publisher is obliged to charge for it. Books much 

 larger, and of many more pages of the ordinary composition, 

 can be afforded at a much less cost. Withal, however, the 

 author commends it to the favorable regard of those to 

 whom it is addressed. 



