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processes that have been described. When his soil, 

 for instance, contains no notable proportion of cal- 

 careous matter, the action of the muriatic acid (7) 

 may be omitted. In examining peat soils, he will 

 principally have to attend to the operation by fire 

 and air (8) ; and in the analysis of chalks and loams, 

 he will often be able to omit the experiment by sul- 

 phuric acid (9). 



In the first trials that are made by persons unac- 

 quainted with chemistry, they must not expect much 

 precision of result. Many difficulties will be met 

 with : but in overcoming them, the most useful kind 

 of practical knowledge will be obtained ; and nothing 

 is so instructive in experimental science, as the detec- 

 tion of mistakes. The correct analyst ought to be well 

 grounded in general chemical information; but perhaps 

 there is no better mode of gaining it, than that of at- 

 tempting original investigations. In pursuing his expe- 

 riments, he will be continually obliged to learn the pro- 

 perties of the substances he is employing or acting 

 upon ; and his theoretical ideas will be more valuable 

 in being connected with practical operations, and ac- 

 quired for the purpose of discovery. 



Plants being possessed of no locomotive powers, 

 can grow only in places where they are supplied with 

 food ; and the soil is necessary to their existence, 

 both as affording them nourishment, and enabling 

 them to fix themselves in such a manner as to obey 

 those mechanical laws by which their radicles are kept 

 below the surface, and their leaves exposed to the free 

 atmosphere,, As the systems of roots, branches, and 



