72 PLAIX AXD PLEASAKT TALK 



field, as grass and its seed is upon the prairies, wheat would 

 grow for a thousand years in succession. The same is true 

 of corn, of potatoes, and of any annual crop. When the 

 annual growth is restored to the soil, it is repossessed of all 

 its treasure which had been loaned for a season. If a part 

 of the crop is removed, the soil is poorer by just so much 

 as the jjortion removed contained within it of the elements 

 necessary to that crop, and it must be restored artificially, 

 i. e. by manuring ^ or by allowing the earth to prepare 

 (by disintegration or decomposition of its minei'als) a new 

 supply ; i. e. by fallowing. A forest will grow for ages on 

 the same spot, for it returns annually its leaves, and, grad- 

 ually, by force of accidents and the elements, its twigs, 

 branches, trunks, etc., to the soil again. But let the whole 

 product be gradually removed, and the soil would soon be 

 xmable to supply the trees their nourishment, except in cases 

 where the soil was very rich in the materials of growth. 

 The forests of Germany, like our mines, are under the man- 

 agement of the government. It was customary, for a time, 

 to allow the peasants the use of the ticigs and smaller 

 branches / but analysis has shown that in these, especially, 

 resides the large proportion of potash entering into the 

 composition of trees ; the annual removal of it debilitated 

 the trees to an extent that obliged the Conservators to 

 change their mode of proceeding. 



On the other hand, in one of Mr. Horsford's letters from 

 Germany, we have the question of growing plants upon 

 their own ashes, brought, by the ablest chemist of the age, 

 directly to the test of experiment. 



" In the spring preceding my arrival in Giessen, Professor 

 Liebig planted some grape scions under the windows of the 

 laboratory. He fed them, if I may use such an expression, 

 upon the ashes of the grape vine — or upon the proper inor- 

 ganic food of the grape, as shown by analyses of its ashes. 

 The growth has been enormous, and several of the vines 

 bore large clusters of grapes in the couree of the season. 



