THE ART OF IRRIGATION. 



115 



afford facilities for the water to sink, but 

 which causes it either to flow off or be 

 evaporated, is not capable of producing 

 any considerable underflow, even when all 

 other conditions favorable to an underflow 

 are present. 



A HAKD SUBSTRATUM. 



As has already been intimated, the exist- 

 ence of an impervious substratum is an 

 essential to the production of an underflow. 

 This applies both to the channel and water- 

 shed of the stream. The want of such a 

 substratum, at an attainable depth below 

 the surface, causes the water to sink down- 

 ward as subsoil water. On the other hand 



an impervious substratum at a reasonable 

 depth, having an inclination somewhat the 

 same as the surface, will intercept the 

 water sinking through the loose surface 

 formation. The downward pressure of the 

 water, together with the impenetrability 

 and inclination of the substratum, will 

 cause the water to percolate in the same 

 direction as the trend of the watershed and 

 channel of the stream. As long as the 

 substratum continues impervious, inclined 

 and sufficiently near the surface, an under- 

 flow, the extent of which depends on the 

 other conditions already discussed, will be 

 found to exist. 



(To be Continued.) 



EXTEA FINE FURROW IRRIGATION, 



But just as cheap and easy as any. Land graded to uniform slope, streams all regular in size and flow. 

 Utilizing ground between orange trees. 



THE ART OF IRRIGATION." 



CHAPTER X. IRRIGATION BY FURROWS. 

 BY T. S. VAN DYKE. 



IN orchard work many of the best irriga- 

 tors run but two furrows to a tree, one 

 on each side, the first year, two on each side 

 the second year, and so on until the third 

 or fourth year when the whole intervening 

 space is filled. Others gridiron the whole 

 ground at once and lead the roots of the 



"Copyright 1895, by T. S. Van Dyke. 



trees away from the trunk and out into 

 the warm, sunlit soil as rapidly as possible. 

 This is the better way where one has the 

 water and time. And where one wants to 

 make the place pay its way from the start 

 one can raise a large amount of produce 

 in the space between the young trees with- 

 out any perceptible injury to them. This 

 is now a common practice in many places 



