512 Mr. R. Hosking on the 



together '01905 cm., twice '01879 cm., and three times 

 *01880 cm., and dividing the sum by 6, we obtain the value 

 '018838 cm. The mean obtained in this way is, I consider, 

 the best value the individual results will produce, taking in 

 account the experimental difficulties in measuring such small 

 bores in the three cases. 



The mean values by measurement were then combined 

 with the values obtained by mercury column, and in this 

 way the final values were obtained. 



Capillary I., circular cylinder, radius '018968 cm. at 0° C. 

 II., „ ,, „_ -018916 



„ III., elliptical cylinder, semi-axes (a) '020762 ,, 



\b) '020076 „ 

 ., IV., „ „ „ (a) '02106 L„ 



{b) '019919 „ 



,, III., mean radius of efflux E( where R 4 = —= — - ) 



\ a 2 + b 2 ) 



= '020413 cm. 

 „ IV., mean radius of efflux R. = '020474 cm. 



An accuracy of 1 in 1000 was aimed at throughout the 

 experiments. The values for the constants in the reduction 

 formula having been obtained, the viscosity was determined 

 from the various observations which had been made from 

 time to time, including those already mentioned. 



A special set of experiments at 0° C. was made at a fixed 

 pressure in order to obtain accurate values of the viscosity 

 at 0° C. The thermometer registered 0°*05 C. throughout 

 the series. With Tube I. in the glischrometer, under a 

 pressure of 197 cms. of water, the average time of flow was 

 109 '7 sees. The first term of the reduction formula was 

 found to be '018690, and the second term '000769. The 

 value for the viscosity at o, 05 was '01792 ; which reduced 

 to 0° C, becomes '01795. A second determination gave the 

 same values practically. The observations and reductions 

 are given on p. 513, also a similar set at 25° C. p. 514. 



Most of the experiments, however, were carried out at 

 50° C. with the water flowing under different pressures. In 

 the following tables (pp. 515-517) are collected the various 

 results. The pressures are given in centimetres of mercury, 

 ihe times of flow in seconds, the values of viscosity (double 

 observations) in absolute measure, and the kinetic energy 

 correction — second term — also in absolute measure. The 

 pressures and times are approximate, and the viscositv 

 values are reduced to the even temperature 50° C. 



