CHEMISTRY OF AGRICULTURE. 407 



A cabbage, which at night is very cold, condenses water to 

 the amount of a gill or more. 



The same operation takes place in the soil. When the air is 

 allowed to circulate among its lower and cooler particles — 

 cooler because shaded from the sun's heat by the earth above 

 them — they condense water as I have just described. There- 

 fore, when, by the aid of underdrains, the soil becomes suffi- 

 ciently open to admit of a circulation of air, the deposit of 

 atmospheric moisture will keep the soil supplied with moisture 

 at a depth easily accessible to the roots of plants. 



If we wish to satisfy ourselves that this is practically correct, 

 we have only to prepare two boxes of finely pulverized soil, one 

 five or six inches deep, and the other fifteen or twenty inches 

 deep, and place them both in the sun at midday in summer. The 

 thinner soil will become completely dried, while the deeper one, 

 though it may have been perfectly dry at first, will soon accu- 

 midate a large amount of water on its lower and more sheltered 

 particles. 



With an open condition of subsoil, then, such as may be 

 attained by .underdraining, we entirely prevent drought. 



It is a source of wonder that, among so many who are plough- 

 ing over this broad land, so few pay any regard to the manner 

 in which they plough — except to have their work as nearly as 

 possible like the work of those who ploughed before them. 

 Now I contend that no man has a natural right to plough who 

 does not first reflect on the reason why he should plough at all. 

 If we were to land on a newly-discovered island, and were to find 

 the inhabitants busily engaged in carrying the stones from the 

 sea-shore to a distant hill, we might consider their course unac- 

 countable ; but if they were to inform us that such had always 

 been the custom of their people, that they had an indistinct 

 notion that it might do good, and that they consider that a 

 sufficient cause for their toil, we should get about as good an 

 idea of the propriety of the affair as we should be likely to get 

 from a genuine old " grandfather-farmer," were we to ask him 

 why he expended the force of his team and fatigued himself to 

 turn the earth bottom side up. 



Ploughing is no child's task, to be hurried over and gladly 

 disposed of. It should be done advisedly and with earnestness. 



