editor's preface. vii 



lands, rendering their manuring more permanent. The dis- 

 covery by the chemist of its mode of action, and the con- 

 siderations arising therefrom, must, however, considerably 

 extend the sphere of its utility, as well as spread the knowl- 

 edge of its powers amongst those at present in ignorance 

 on the subject, and also afford instruction as to the most 

 economical use of so powerful an absorbent of manure ; 

 for instance, it may be added with great advantage as an 

 ingredient to the compost-heap, if spread in very thin lay- 

 ers, so as not to impede the circulation of decomposing heat 

 through the mass. 



The views of Dr. Stockhardt on nearly all the chief 

 points of the preparation, action, and values of manures, 

 their consolidation and perfect protection, agree so exactly 

 with those which have been offered to the public by the 

 editor in various addresses delivered by him within the last 

 few years, that he cannot but congratulate himself on the 

 support of his opinions by a scientific writer of such ac- 

 knowledged talents, particularly as no communication has 

 ever passed between them. Even the discussion of those 

 points on which a difference of opinion exists, such as the 

 value of fresh manure spread on the land, &c., must tend 

 to elicit truth. 



The same may be said of his exposition of the value of 

 guano, experiments on which were exhibited here publicly 

 by the editor in 1842, and on the value of which manure 

 he published a pamphlet in 1845, not a word of which 



