DR. SCHLEIDEN'S THEORY OF AGRICULTURE. j (Jl 



cultivation of other plants, so that a greater number enters into 

 the question. Hence a second subject of inquiry, in what order 

 ought these to succeed each other ? 



The first question needs no further observation. The second 

 is unfortunately one of great difficulty, for the solution of which 

 but few data exist at present. Experience informs us that two 

 crops of a similar nature should not succeed each other, and 

 science at present can do no more. The matter of greatest con- 

 sequence will always be with what plant to begin the course. 

 Inorganic matters ought not only to be present in the soil, but 

 in the right proportion. The worst method then should seem to 

 be to begin with the potato, the contrary practice for so many 

 years being probably one of the main causes of the present 

 depraved state of the plant. The choice must be directed by a 

 comparison of the inorganic constituents of the dung with those 

 of the plant proposed, so that that plant will be taken first which 

 on analJ^sis bears the nearest proportion to that exhibited by the 

 manure. If then the inorganic contents of the harvest be sub- 

 tracted from those of the manure, the second plant will be chosen 

 according to its relative proportions, and so on through the 

 whole of the course. Now, if we compare the contents of ordi- 

 narj' manures with those of agricultural plants, we shall find that 

 potatoes and wheat are those which have the most distant relation. 

 They are those which are subject to most diseases. If the com- 

 parison be continued, and attention be paid to the proportion of 

 the most influential constituents, namely, the phosphate of lime 

 and magnesia to the sulphuretted and muriated ali<alies, we obtain 

 the result that of all plants rye is the best with which to begin 

 the course, which agrees with the opinion of many practical men, 

 that rye is most suited to fresh manure. 



It must, however, be taken into consideration, that in rotation 

 of cropping changes in the physical condition of the ground are 

 effected which are of as much consequence as the proportion of 

 tlie inorganic constituents, .so that the choice is much contracted, 

 and comes indeed to a question between cereals and other 

 agricultural plants. 



The above attempt to give a fair and useful abstract of a 

 work certainly entitled to consideration will, it is hoped, be 

 suggestive of much that is valuable, and throw light on some 

 points on which a great deal of confusion exists at present. The 

 almost total absence of reference has made it occasionally a 

 matter of some difficulty to arrive at the exact meaning of the 

 author. It must be borne in mind that the argument proceeds 

 on a system of cultivation not altogether coincident with what 

 we are ourselves accustomed to, and that consequently a little 

 allowance on that score must sometimes be made. 



