VISCOSITY OF WATER BY THE EFFLUX METHOD. 123 
no correction is necessary for temperature, so far as the dimensions 
of the apparatus are concerned, assuming that their original 
evaluations are all for the one temperature. This is evident if 
we consider the effect on the elements of the fundamental formula 
(4). For supposing the factor (1 + ¢) to express the linear correc- 
tion for expansion for the particular temperature to which all the 
parts are subject, then, on substituting for ¢ its equivalent Q/T, we 
shall have! 
eee Cty rt hi ie 
SL(I+He+O* 8Le 
This indicates the desirableness of securing this condition. 
7 
Evaluation of the viscosity at 10°C. from Poiseuille’s experiments. 
—The results of the computations for the values of the viscosity 
at 10°C. are giyen in the table in§ 9. It is worthy of remark 
that the satisfactory determinations depend on tubes whose radii 
and lengths range between somewhat wide limits, viz., 
R=0:0006975 L=0125em. Tube 1, 
£=0-032537 L=38-382 Tube / 
that is, for the radii the range is from 1 to 47, for the lengths 1 
to ‘$0. The whole series of observations given in one of 
Poiseuille’s tables is involved in the determination of 1 wherever 
the extrapolation method—formule (6a) and (6b) § 8—has been 
used. These cases are distinguished in the table by the absence 
of an asterisk. Those marked with an asterisk give the mean 
result deduced from the first three members of the series,” as I 
TEU ieeremeese ee a 
oe uille’s method of reduction, vide his memoir, § 142 - 144, p. 526 
rading =~ pn y unnecessarily operose, i oneous. He applies the 
the } ange (1 + ¢)* and the volume correction (1 + ¢)*» but neglects 
inten ee orrection (1 + (): see his note p. 525. He computes the mass 
2 The 
ASS cahelie three exceptions to this statement. There is only one 
tem t each, in the case of tubes M, and Mi. In the case of 41 the 
of the first experiment was not 10°, so that the following 
ee were taken. 
* 
