IV PREFACE. 



lead him on, till be ends by an eager study of the 

 larger treatises. 



In the general arrangement of the chapters, I have 

 followed that marked out in Prof. Johnston's admirable 

 Catechism of Agricultural Chemistry and Geology. 

 The expressed opinion of many teachers, " that the 

 catechetical form was not adapted to the schools of 

 this country, and that they needed a work of more 

 fullness and detail," induced me to think of an effort 

 to supply their wants. 



The approbation bestowed by the New- York State 

 Society upon the essay, which, with some additions 

 and alterations, has assumed its present shape, led to 

 a more speedy completion of my half-formed plans, 

 than I had anticipated. 



The teacher will perceive that the experiments, and 

 the illustrations, occasionally recommended, are of the 

 most simple character. No expensive materials are 

 needed, and, excepting a few cheap chemicals, almost 

 any house could furnish every requisite article. 



No questions are appended to the chapters, for the 

 reason that they would be a disagreeable interruption 

 to the general reader, and would perhaps confine the 

 teacher to a routine in his examinations. The chap 

 ters are, however, divided into sections and para 

 graphs, in a way calculated to fix the attention of the 

 reader upon leading points. 



Questions should be asked with the distinct inten 

 tion of impressing at least the chief conclusions and 



