FLO WAGE IN SUBCAPILLARY OPENINGS. 143 



therefore no addition to the ground waters During that time the water 

 table fell in the granitic sand, on an average, at the rate of 0.38 meter per 

 kilometer per annum. This fall of water during these years in the granitic 

 sands alone, Mr. Lippincott says, is sufficient to account for the entire dis- 

 charge of the Los Angeles River. A head of 9.4 meters per kilometer in 

 large channels where friction is small would result in the outpouring of the 

 great quantity of water held in the gravels into the Los Angeles River in a 

 very short time. But the openings in the sands are capillary, and the resis- 

 tance due to friction and to viscosity is such that the water was very slowly 

 delivered to the river under a head of 9.4 meters per kilometer, the average 

 fall being, as explained, 0.38 meters per kilometer per annum. 



Movement as slow as this must be rapid as compared with the exceed- 

 ingly slow movement of the ground water in the artesian basins referred 

 to. It follows from these illustrations that the ordinary rates of movement 

 in the belt of cementation are very much slower than were the move- 

 ments under the conditions in which Poiseuille, King, and others carried 

 on their experiments. It is plain that the laws derived from experiments 

 as given by Poiseuille and King in reference to capillary flow are only 

 very partially applicable to movements of ground water; indeed, their 

 application is probably limited to the somewhat rapid movements of the 

 water in the capillary tubes above the level of ground water in the belt of 

 weathering- where gravity has its full effectiveness, and adjacent to large 

 openings, either natural or artificial. 



subcapMary openings. — By subcapillaiy openings, as already explained, are 

 meant openings smaller than capillary openings. In subcapillaiy openings 

 the attraction of the solid molecules extends from wall to wall, and there- 

 fore in these openings the water is wholly that of the films attached to the 

 walls by molecular attraction. There is no free water, in the sense that 

 the molecules are free to move among themselves, resisted only by the vis- 

 cosity of the fluid. The ratio of the resistance to movement of water thus 

 attached as films to solids is almost infinitely great as compared with that 

 of free molecules. Water thus attached is as if glued to the walls. 



Quincke has determined that the attractive influence of glass upon a 

 fluid extends through a silver film 0.00005 mm. thick; or, stated in another 

 wav, he finds that the distance through which molecular attraction acts is 



