84 TORRENTS. 



If now you turn the same force of water on a cultivated field, and let 

 it find its own outlet, at the same distance as in the grass, you will find 

 the flow stop almost the minute you turn the water off. I have tried 

 this in a number of cases. It is easy to try and it is a striking illus- 

 tration of what a difference in water delivery there is between bare land 

 and grass. I tried this experiment in a larger way on my ranch. 

 There is there an orchard in the canyon. Storm water rushed through 

 this, cutting in some places and depositing several feet of detritus in 

 others. I had this storm water conducted out of a channel it was cut- 

 ting and turned into a eucalyptus grove. The stream was immediately 

 sub-divided; its load of sand was dropped in a miniature cone, the 

 water was absorbed; the torrent rushing into this grove was extin- 

 guished. The water absorbing power of the Sierra Madre range, with 

 its chaparral covering is almost incredible. Steep as the range is at 

 my place, I have only once seen a rainfall delivery across the ranch ir 

 the wash of the three canyons. It is very rare that storm off-flow oc- 

 curs in these canyons at all. The brush till last year had been without 

 fire for probably over forty years. The springs have been celebrated 

 for their volume and regularity. The rainfall was absorbed in the 

 mountains almost entirely and slowly percolating to more open quartz 

 ledges, flowed through these to the springs. All the quartz ledges are 

 curiously and conveniently faced on the south and lower side with a 

 water-proof dyke. Mr. Koebig, the distinguished engineer, who has 

 made such a study of the San Gabriel water-shed, indicates what an 

 enormous difference in the Sierras forests or no forests make in their 

 water-holding power. Mr. Koebig states that this fearfully denuded 

 water-shed has a storm off-flow of over 95 per cent, in some places, 

 while it ought not to be over fifty. He speaks of his own observation 

 of the increased storm off-flow from a canyon just burned. He also 

 compares the reduced summer flow due to storm off-flow from this 

 great and much-injured water-shed with the summer flow from the 

 small water-shed of Lytle creek, which has been but slightly injured. 

 Lytle creek, with less than a third the water-shed, has about the same 

 summer flow as the San Gabriel. This Lytle creek is also far more re- 

 liable and steady. Neither has Lytle creek anything like the destruct- 

 ive torrent power of the San Gabriel. 



An interesting illustration of the soil-holding power of humus 

 can be observed in a forest and on a road in a forest. Where the 

 ground is covered with humus, you will find no mud. The soil does 

 not stick to your shoes. The road soil, if wet enough, will stick to 



