VISCOSITY OF WATER BY THE EFFLUX METHOD. 91 
take the mean values for Poiseuille’s tubes the ratio of whose 
radii varies between the limits 1 and 47. 
Glass Tubes. Meanof. Rapprox.c.m. 4,at10°C. Authority. 
M M, (2) 0007 01313 Poiseuille 
EE, (2) 0015 01341 do 
D-D, (4) 0022 01305 do 
C-C, (4) 0042 01308 do. 
B-B, (4) 0056 01310 do 
A-A, (4) 0071 01308 do 
F-F, 3) 0326 01315 do 
The constancy of 1, shows that it must be supposed identical with 
7, that is to say @ is zero for cases of efflux through glass tubes, 
as indeed is admitted by Helmholtz.1 Nor does a more extended 
comparison of values similarly deduced lead to a different con- 
clusion. In the table hereunder tubes of different materials are 
included, and of larger radius, that of the greatest being 907 times 
that of tube M above. 
Tube. No. Expts. Rapprox.c.m. 7 at 10°C. Authority.” 
Glass 1 0140 01400  _Hagenbach 
” 0172 701320 Grotrian 
D 0182 01318 ‘ 
; 2 Q198 01311 Konig 
3 0199 01291 ‘ 
ss 4 0290 01331 Slotte 
Copper 2 0297 01356 Couette 
Glass 4 0302 01319 Wagner 
z 1 0309 01400 Hagenbach 
White metal 3 0504 01341 Couette 
Inge 1 “0525 01324  Hagenbach 
m 1 0550 01287 ‘s 
Paraffine 3 0685 01360 Couette 
Sait On ee eee 
1 Sitzber. Wien. Acad. Bd. 40, p. 654. 
2 These values I have reduced from the data published by the investi- 
gator whose name is appended. The same remark applies to the preced- 
"2 values obtained from Poiseuille’s experiments. 
