in Free Surfaces of Liquids. 



147 



ex 0-9973 



0-9852 



0-9110 



0-7904 



a 8-000 



5-657 



2*947 



2-354 



where a denotes the specific gravities, and a the cohesion- 

 constants. 



In order to see on what the resistances to the motion of the 

 plate in the interior of the liquid chiefly depend, I determined, 

 with the aid of an oscillating brass disk, the coefficients of 

 friction of some of the liquids employed, according to the 

 formulas and rules given by O. E. Meyer*. They are collected 

 in the following table, in which I have confined myself to 

 giving their relative values referred to water. The tempera- 

 ture amounted to 21° C. ; only with sulphide of carbon was it 

 lower, and that in consequence of the hardly to be avoided 

 evaporation. Since the absolute values of rj for distilled 

 water, 



According to O. E. Meyerf, at 21°-6 0-01190, 



According to GrotrianJ, at 21°'5 0-01250, at 21°*58 0'01236, 



are known, the friction-coefficients of the other liquids can 

 easily be calculated from the following table. 



Table VII. 





P- 



7]. P . 



n> 



X 



Sulphide of carbon . . . 

 Oil of turpentine 



1-293 



0-870 



0-7937 



0-8720 



0-9023 



0-9737 



1000 



0-4262 



2-030 



1-055 



2-282 



2-720 



1-721 



1-000 



0-3297 



2-333 



1-329 



2-617 



3014 



1-767 



1000 



0-782 

 1-859 

 1-063 



1-000 





" 





Water 





A comparison of the values of rj . p with the ratios of the 

 resistances ^ shows, as was to be expected, no perfect agree- 

 ment. Much rather, in the resistances the specific gravity of 

 the liquid has also some influence. The peculiar behaviour of 

 the mixtures alcohol and water, which possess a maximum of 

 r) } has moreover been already observed by Poiseuille§. 



Halle a. d. S., Aug. 1, 1880. 



* Pogg. Ann. cxiii. 1861. 

 X Ibid. clx. p. 242 (1877). 



t Ibid, cxiii. p. 399. 



§ Ibid, lviii. p. 437 (1843). 



