12 IRRIGATION. 



is influenced by the moist winds of the ocean, and the 

 fogs from the Gulf Stream. The evaporation from the 

 soil is therefore reduced to a minimum, and the light 

 rain-fall, more constant than with us, and consisting of 

 frequent light showers, is ample for the needs of vegeta- 

 tion. On the contrary our climate is continental and 

 subject to the influence of dry winds, and a higher 

 temperature, and our heavier but more inconstant rain- 

 fall is found inadequate. Hence our low average of those 

 crops which need a large quantity of water for their max- 

 imum growth, and hence the ineffective efforts of Ameri- 

 can farmers to reach the high averages of the crops grown 

 in England. 



Some very interesting experiments showing this rela- 

 tion between the weight of grain produced and the quan- 

 tity of water consumed by the plants, whether evaporated 

 through their leaves, or appropriated by their tissues, 

 were made in 1874, at the Agricultural Observatory of 

 Montsouris, France. The grain grown was wheat. Sev- 

 eral kinds of soils and fertilizers were used, which gave 

 very varying results, but the variety in the amounts of the 

 product was remarkably illustrative of the facts proved. 

 The means adopted for determining the results were the 

 most complete, and there is no reason to doubt the entire 

 accuracy of the conclusions reached. The results are 

 given in the following table : 



L Table showing the total quantity of water evaporated and the grain pro- 

 duced; also the quantity of water consumed for one pound of grain in 

 nine experiments with various fertilizers. 



Pounds of water Pounds of grain Pounds of water 



evaporated. produced. for one of grain. 



No. 1 1,616 0.6 2,693 



" 2 1,512 0.8 1,890 



3 4,703 2.4 1,960 



" 4 2,202 2.7 816 



" 5 3,262 2.9 1,125 



" 6 4,327 3.1 1,396 



" 7 4,751 5.5 864 



" 8 7,417 9.2 806 



" 9. 7,702 10.6 727 



