256 SCIENCE PROGRESS 



a period has taken place in the past. Without doubt the 

 climate chiefly affects a crop by the variations it induces in 

 the water content of the soil, a factor which also depends upon 

 the physical texture of the soil and the treatment to which it 

 is subjected. A certain amount of attention has been given to 

 these points at Rothamsted in the past : for example, deter- 

 minations have been regularly made of the amount of water 

 percolating through the soil, of the effect of the growth of plants 

 upon the water content at different times of the year and, again, 

 of the changes in the texture of the soil — which determines 

 both its retentiveness and permeability — caused by the long- 

 continued applications of particular manures. It is probable, 

 however, that investigations of this kind will play in the future 

 a more considerable part, as the importance of the physical 

 behaviour of the soil begins to be recognised by scientific men. 

 We have to remember that the labours of the farmer in the 

 spring are almost entirely directed to getting the soil in a 

 particular physical condition ; that which he calls " a good seed- 

 bed " and the subsequent growth of the crop will depend far 

 more upon the mechanical texture it has acquired than upon 

 the amount of manure it may receive. When the farmer speaks 

 of the field as having been exhausted by the growth of a crop of 

 wheat he refers far more to the bad mechanical condition it has 

 reached than to the comparatively small withdrawal of plant- 

 food, and most of the objections which from time to time have 

 been taken by farmers, with reason on their side, to particular 

 artificial manures are really due to their secondary effects upon 

 the tilth of the soil. In the importance which is now being 

 given to the physical aspect of the soil we see again how far 

 we have travelled from the early conception of the soil as a 

 mere magazine of ready-formed food which prevailed for some 

 time after the Rothamsted experiments were started. It would 

 be possible to go on indefinitely indicating what work remains 

 to be done and what problems are still unattacked in such a 

 well-worn subject as to the relation of the plant to the soil ; 

 sufficient has been said to show how big the task is before 

 the farmer can acquire anything like the control of the soil 

 which the manufacturer, either of metals or of textiles, possesses 

 over his materials. /This control is likely to be more necessary 

 to the English farmer than to any other : in no other country 

 is the price of land so high nor the pressure of the population 



