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water may be " combed " out from the fog. In the effectiveness 

 of this filtering process, which is said to be a good method for 

 removing water from the fog, lies, I believe, an important reason 

 why the redwood loves the zone subject to fogs. And it will be 

 readily seen that this factor not only increases the general amount 

 of moisture in the region, but it supplies the redwood itself with 

 a proper amount of water at a time when there is the least rain- 

 fall, that is, in the late summer and early autumn, when the fogs 

 are especially abundant. 



So far as I know, there is no method in use for determining 

 the amount of fog precipitation. The amount of water in a fog 

 which extends vertically iooo feet may be equal to o. I inch rain- 

 fall.* But, of course, only a small portion of this is precipitated. 

 This amount, however, can be greatly increased if the fog is 

 passed through such a filter as is formed by a redwood forest, 

 and under such conditions the amount of water taken out of the 

 fog by the trees is considerable. Two or three illustrations will 

 show this at least approximately. I have been told by a gentle- 

 man who owned a large ranch in the redwood belt, and whose 

 observation was quite trustworthy, that whenever there was a fog, 

 especially if accompanied by a wind, the soil beneath the trees ap- 

 peared as if drenched by a heavy rain ; and that, further, in cases 

 of fires in his forest, if a fog came up accompanied by wind, the 

 fires could be brought under control. To any person who has 

 seen the force and destructiveness of a forest fire this observation 

 will appear very significant. The relation of the redwood to fog 

 precipitation is shown in another way, which, although suffi- 

 ciently bizarre in itself, is vouched for, and may lend a hint to a 

 possible manner of estimating the amount of water precipitated 

 in this manner. On the "hog-back" of the Santa Moreno 

 mountains lives a woodchopper, in a place once heavily covered 

 by a redwood forest, but where there is left only an occasional 

 large tree. Like other mountaineers, he must use water for culi- 

 nary purposes at least, and in lieu of a convenient spring or well 

 he has devised a unique " tree- well." The chopper has fashioned 



* Alexander McAdie, Fog Studies on Mt. Tamalpais. -Pop. Sci. Monthly, 59: 

 535. O. 1901. 



