DR. SCHLEIDEN'S THEORY Ol- AGRICULTURE. 147 



and therefore through one and the same effort to satisfy as many 

 conditions as possible, tlie evil consequence of which is, that the 

 multitude of ends to which it is directed, from the unequal de- 

 gree in which every particular object is attained, make it ex' 

 treraely difficult to estimate beforehand the results of our 

 labours, so that it requires great knowledge and circumspection 

 to jjlace them in their due relation witli the preceding operations. 



All, then, that can be done in the present state of things is to 

 examine such methods of cultivation as have from time to time 

 been adopted empirically, and consider on what conditions of 

 vegetable life they operate, which they improve and which they 

 vitiate ; and to this end we have first to review- briefly the indi- 

 vidual circumstances on which success depends, and secondly, on 

 how many of these conditions, in what way and to what degree, 

 every particular method of cultui'e has any influence. 



The circumstances on which the success of agriculture de- 

 pends may be diviiled into two classes, those over which the skill 

 of man has no control, and those which he is able more or less 

 to modify. The first comprises climate, atmospheric conditions, 

 and the geologic nature of the substratum ; the latter the phy- 

 sical nature of tlie soil itself and its chemical constitution. 



I. — A. The dependence of vegetation on climate is too pal- 

 pable to be denied, and yet the cultivator has but little, except 

 his own tact and common sense, to assist him. In countries 

 where there is such an amazing difference between different 

 years, careful and conscientious records of the course of seasons, 

 with the help of a little physiological and geological knowledge, 

 would throw great light on the value of an estate and its capa- 

 bilities. In Germany there is sometimes all the luxuriance of a 

 subtropical country, while in other years the produce is almost 

 nominal. 



The further Ave go towards the equator or pole the more uni- 

 form is the climate and the fewer the species under cultivation. 

 In consequence of the irregularities jieculiar to the more tem- 

 perate regions, a greater diversity of objects and modes of cul- 

 tivation is possible and indeed necessary, and therefore more skill 

 requisite. 



Mere prognostics of weather are worse than fallacious. Care- 

 ful observers may indeed in their own particular districts look 

 forward safely from past experience to the state of the weather 

 for a day or two, but beyond this there is not even any tolerable 

 degree of probability in their predictions. That there are, how- 

 ever, certain cycles of seasons is far from improbable, but these 

 can only be ascertained by careful and honest registration through 

 a long series of years. 



If, however, we could know beforehand that in ten throws of 



