FLO WAGE IN CAPILLARY OPENINGS. 141 



factor. The relative viscosity of water at various temperatures below 

 100° C. is as follows:" 



Relative viscosity of water at different temperatures. 



0° 100.00 



15° 63.60 



30° 44. 90 



45° 33.89 



60° 26. 94 



75° 21. 75 



90° 18.16 



From this table it appears that the viscosity of water at 45° C. is about 

 one-third its viscosity at 0° C; at 90° C, less than one-fifth as great as 

 at 0° C. It therefore follows that temperature is a factor of the greatest 

 importance in the flowage of water through capillary openings in the litho- 

 sphere. It is shown (pp. 138, 145-146) that the openings in the lithosphere 

 are largely those of capillary or subcapillary size ; hence the importance of 

 the temperature element. 



Another factor entering into the flowage of ground water is the 

 influence of the meniscus where the openings are not fully occupied by 

 water. Wolff 6 has shown that if water be introduced into an empty 

 capillary tube, the meniscus in advance of the column is an important 

 retarding influence, and consequently that the movement is slower than 

 under circumstances where there is no meniscus. This influence is likely 

 to be important in many cases in the belt of weathering, where partial 

 filling is the rule, but is probably of little consequence in the belt of 

 cementation below the level of ground water, where saturation is the rule. 



In conclusion, it should be fully understood that the laws of capillary 

 flow, as developed by Poiseuille and others, involve rather rapid movement 

 through the capillary openings. It has already been stated that viscosity 

 of the solutions and friction between the moving and the fixed water are 

 the determinative factors in reference to capillary flow. It is highly 

 probable that where the movements are very slow the friction is minute or 

 inappreciable and that the consequent departures from Poiseuille's laws are 

 very great. Apparently in the exceedingly slow movements of many of 



«Landolt and Bornstein Tabellen, 1894, p. 288; supplemented by experimental data furnished by 

 Mr. C. F. Bowen. 



6 Wolff, H. C, The unsteady motion of viscous liquids: Trans. Wisconsin Acad. Sci., Arts, and 

 Letters, vol. 12, pt. 2, 1900, pp. 552-553. 



