LIQUIDS AND ALLIED EXPERIMLXTS. 



59 



and tube. Inasmuch as the forces are known, it may be v»orth while to 



test the method for measuring the viscosity of the liquid. Table i6 and 



those which follow contain the date, the corresponding value of t'o, and the 



other data needed to compute k by equation (5). }J denotes the mass of 



the float, pg its density, p^ the density of the liquid at the temperature given. 



Diameters of vessels are referred to under 2r; h' , h" , h'" are the vertical 



heights of bubble, the water head for the diver ^vhen sunk, and the effective 



height of the water level within the diver, above its mouth. The head //' 



is liable to vary in the lapse of time. 



Table 16. — Air-air through water. Ve.ssel -4 (double tube). j/= 12.011; p^ = 2.484; 

 C=43.i4; float, 2r = 2.95; tube, 2r = 3.3; vessel, 2/- = 4.4. /;'=i.S, /i" = 4.7, 

 /j"'=7.o. 



The present case of diffusion of air through water in the double-tube 

 apparatus is rather a disappointment in comparison with the long series of 

 results obtained above with the single-tube apparatus, inasmuch as the 

 diffusion after all allov/ances are made for differences of constants takes 

 place much faster than in the original experiment. Fig. 17, moreover, 

 apart from fluctuations due to variation of solution with temperature, 

 shows two different rates, the slower in September preceding a in figine and 

 the faster in October, following a, whereas no variation whatever had taken 

 place in the apparatus to our knowledge. It is very difncidt to interpret 

 this, for it is hardly conceivable that any appreciable cliange of equivalent 

 importance should have occurred in the air of the room. 



The excessive rate of diffusion here observed occurs for the case where 

 the diffusion column is narrowed throughout, to a nearly constant diameter 

 as compared with the large diffusion column above the swimmer which 



