1068 
d. Ether, at 11°,2 (u = 0,725, n = 0,002785) 
a= 0,01 ¢ + 19,95 .10—* #°—18,66 , TO! 2 + 8,5. 10—* pl, 
with 7’= 20,76 and Jd = 0,04840. 
e. Liquid air, at 80°,8K = — 192°,3C. (u = 0,956, 7 = 0,001718) 
a= 0,01 2 + 15,82. 10-* 2*—12,88.10—* 2 + 5,8. 10-1" 27, 
with 7’— 20,72 and 0 = 0,04194. 
The angles of deflection are expressed in radians. The formulae 
are drawn up in such a manner that the time is reckoned from the 
moment at which a= 0,01 («a =—1; scale-deflection 3.074; at these 
very small amplitudes the influence of the higher terms practically 
disappears); they are derived from observations between the limits 
a= 1 Vand a=—,008) 
Considering the absolute accuracy of the scale-readings (see above) 
it follows, that the influence of the higher terms does not make itself 
felt with water till «—=1,6 or a=0,016, with benzene a little 
sooner, with carbon disulphide and ether at a=0,011 and with 
liquid air at «0,012. These few data are sufficient to show, as 
was to be expected (see § 1, note), that for one and the same oscil- 
lating system the limit for practical infinite sma!lness of the velocities 
lies in general the lower the smaller the viscosity of the liquid. 
In order to confirm this result by another experiment with a liquid 
of higher viscosity an observation was made with a mixture of 
water and glycerine: 
f. Mixture of water and glycerine, 11° C. (u = 1,087, 1 = 0,02825) 
a = 0,01 # + 3,27. 10° #°—1,01 ,10—*. 2°, 
with 7’= 21,10 and d= 0,2623. The deviation actually begins here 
at a higher limit than with pure water, viz. at a—0,021. 
In the computation of the viscosities account had to be taken as 
formerly (Comm. N°. 1495, V) of the friction of the air for the not- 
immersed parts of the apparatus and of the internal friction of the 
wire. For this purpose an experiment was made in ordinary air, but 
without the sphere *) and with a copper cylinder instead of the 
aluminium one (see Comm. N°. 1494); in this experiment the obser- 
vations were again extended between the same wide limits as in 
the previous experiments. . 
go Air ==, p= 165 mm LL: Ò == 0,00606, 
“== 0,01 # 98,8 10-2" = 1658 10 
1) This experiment cannot therefore be compared with the previous ones, where 
the friction acted chiefly on the sphere. 
