ground after barley to remain at rest for two years in 

 grass ; sows peas and beans on the lays ; ploughs in 

 the pea or bean stubble for wheat ; and in some in- 

 stances, follows his wheat crops by a course of winter 

 tares and winter barley, which is eat off in the spring, 

 before the land is sowed for turnips. 



Peas and beans, in all instances, seem well adapt- 

 ed to prepare the ground for wheat ; and in some 

 rich lands, as in the alluvial soil of the Parret, men- 

 tioned in the Fourth Lecture, and at the foot of the 

 South Downs in Sussex, they are raised in alternate 

 crops for years together. Peas and beans contain, as 

 appears from the analyses in the Third Lecture, a 

 small quantity of a matter analogous to albumen ; but 

 it seems that the azote which forms a constituent part 

 of this matter, is derived from the atmosphere. The 

 dry bean leaf, when burnt, yields a smell approaching 

 to that of decomposing animal matter ; and in its de- 

 cay in the soil, may furnish principles capable of be* 

 coming a part of the gluten in wheat. 



Though the general composition of plants is very 

 analogous, yet the specific difference in the products 

 of many of them, and the facts stated in the last Lec- 

 ture, prove that they must derive different materials 

 from the soil ; and though the vegetables having the 

 smallest systems of leaves will proportionably most 

 exhaust the soil of common nutritive matter, yet par- 

 ticular vegetables when their produce is carried off, 

 will require peculiar principles to be supplied to the 

 land in which they grow. Strawberries and potatoes 

 at first produce luxuriantly in virgin mould recently 



