PUBLISHERS' NOTE. 



The profound interest felt in liis subject by tbe author of this 

 work, induced him to devote to a careful revision of it all that 

 portion of the last year of his life which his official duties and his 

 failing strength left at his command. Every new book within 

 his reach, bearing in any way on the topics treated in this volume, 

 was f aithfuUy consulted, every opportunity for personal observa- 

 tion conscientiously seized; and, although neither leisure nor 

 health permitted so full a use of these works, nor so frequent re- 

 course to the great book of Nature, as was desired, yet, whenever 

 a new argument or a new fact led to the modification of a 

 previously expressed opinion, such modification has been frankly 

 made. 



On the whole, however, it wiU be seen that the author's general 

 conclusions remain unchanged, and his conviction of the vital 

 importance to the future of our race of a wiser economy, on the 

 part of the present and rising generation, in the use of Nature's 

 gifts, was only deepened and strengthened by the study and ob- 

 servation of every additional year of his life. 



The hope of impressing, in some degree, this conviction upon 

 the minds of those in whose hands the practical value of his sug- 

 gestions Hes, was the inspiring motive of the work in its begin- 

 ning, and the motive which continued to animate the writer to 

 the last day of his earthly life, a considerable portion of that day 

 being devoted by him to the completion of this revision. 



