448 MESSRS. T. E. THORPE AHD J. W. RODGER ON THE RELATIONS 
determined with one pair of tubes should be on the average about 0'2 per cent, 
greater than those determined by the other pair if the correction were operative. 
No such difference is apparent ; hence the value of the correction probably falls 
witbin the limits of the experimental error. 
Sprung (loc. cit.) gives a series of values for water extending from 0° to 50° which 
are expressed in gravitation measure. On introducing the necessary corrections to 
reduce these values to dynes, we find that from 0° to 15° they are practically identical 
with ours; from 20° to 50° they are slightly larger, the deviation increasing as the 
temperature rises, until at 50° it is about 0'9 per cent. At 40° and 45° our curve 
passes between those of Sprung and Poiseuille. The Couette correction would 
diminish Sprung’s results by about 0‘46 per cent. 
IloSENCRANZ [loc. cit.) made a series of observations on water, at temj)eratures 
between 40° and 90°, with a view of supplementing Poiseuille’s observations 
between 0° and 45°. On plotting Rosencranz’s values it is at once seen that 
individual results differ widely from the values deduced from a mean curve. At the 
higher temjoeratures, the mean values are also considerably higher than those obtained 
by Slotte (v. infra) and ourselves at these temperatures. Rosencranz’s value at 
42°9 is identical with ours at that temperature, but at 80° his result differs by some 10 
per cent, from that of Slotte and ourselves. The discrepancy between PtOSENCRANz’s 
values and those of later observers is to be ascribed to the imperfections of his 
experimental method. There can be little doubt, from the construction of his 
apparatus, that lie failed to ascertain the real temperature of the water flowing 
through the capillary tube. 
Slotte {loc. cit.) is the only observer who has hitherto attempted to determine the 
viscosity of water at all temperatures between its ordinary freezing and boiling-points. 
His results are expressed in dynes, and we have modified them by substituting the 
Couette-Finkener values of the kinetic energy correction for those of Hagenbach. 
This makes a difference of about 1 per cent, in the value of t) at the higher tempera¬ 
tures. At 0°’2, Slotte’s value tor'll differs by about 1'5 per cent, from ours; at 
higher temperatures, his numbers are about Off per cent, greater. The application of 
the correction for friction effects outside the tube would diminish his values to the 
extent of about 0’4 per cent., i.e., make them about O'o per cent, greater than our own. 
Traube {loc. cit.) gives two sets of values for -q, determined with two different 
tubes, at temperatures between 0° and 60°. At the same temperature, the observa¬ 
tions of the one series agree to within 1 per cent, with those of the other. Traube 
compares his numbers with those of Poiseuille (as given by Hagenbach), Sprung, 
and Slotte. From this comparison T’raube’s values appear to be larger than 
Slotte’s by amounts varying between 2 and 3 per cent,, but agree mm’e closely with 
those of the other observers. This agreement, however, is not real, since Poiseuille 
and Sprung’s values are expressed in gravitation measure. As a matter of fact, when 
the results of all the observers are expressed in dynes, Traube’s numbers differ more 
