No. 105.] 231 



only be known by their effects in practice, or by analysis. But these 

 considerations more particularly demand attention in cool and moist 

 climates, as in Britain, where the simple application of water is un- 

 important. Hence there autumn and winter irrigation is much prac- 

 tised the water being then charged with animal and vegetable matters 

 which have accumulated during the summer. In the United States, 

 where a supply of water during drougth and heat is so much more 

 essential, this difference in the richness of water is not so visibly 

 observed. 



In using small streams, on considerable acclivities, by catch-work 

 as represented in fig. 1, temporary means of diverting the water from 

 the main channel may be resorted to, and there can possibly be a failure. 

 But in larger streams, the work should always be well formed at 

 once. A good permanent dam must be made, and substantial hatclies^ 

 or solid framework furnished with a sliding gate, inserted. In using 

 small streams, many diverging channels may be cut ; in large ones 

 this cannot be done, from the cost of many large dams ; a single 

 dam may therefore be used, from which a main side channel should 

 pass, to be subdivided according to the circumstances of the case. 



Irrigation will always need an exercise of the judgment, to be done 

 in the best manner ; no two pieces of land being exactly alike, and 

 the irregularities of the surface varying in many ways, the plan of 

 the work, or the distribution of the channels must vary. Each, 

 therefore, requires a different design, adapted to the circumstances 

 of the case. But no one should be deterred from an attempt, nor 

 lose the eminent advantages of irrigating his grounds, because he 

 cannot attain perfection at once. 



It is sometimes objected to watering grass and other lands, that 

 the crop, though greatly increased in quantity, is lessened in quality. 

 This is indeed true to a small degree, but not more so than results 

 from an increased growth by stable manure. The slight inferiority 

 in quality is immeasurably overbalanced by the increase in bulk. No 

 objector would desire his hay crop to be lessened one-half in quantity 

 by a parching drought, in order that the hay might be better. 



Application to different crops. — Irrigation is usually applied 

 to grass land, but there appears to be no reason why it may not be 

 greatly advantageous if used for different cultivated crops during our 

 hot summers. S. Williams, of Waterloo, N. Y., states that during 



