502 Mr. R. Hosking on the 



multiplied by ?\/r . In this instance r x jr 2 was 1*61 and 

 E/C = r s /r 1 .^2 = 2-485 or E = 30,800,000 and Poisson's 

 ratio = -243. 



A tension-test on a similar piece of tube gave E = 30,700,000. 



In addition to its applications for bending and twisting the 

 apparatus may be used for testing a variety of cases of com- 

 bined stress if a pump is added to give a fluid pressure in 

 the interior of tubes. 



The accompanying diagram (PL XI. fig. 10) shows the 

 results of tests to failure of bicycle-tubing when subjected to 

 (I.) bending, (II.) twisting, and (III.) twisting combined with 

 a uniform bending moment. 



XL VI. The Viscosity of Water. 

 By Richakd Hosking, B.A. (Camo.)* 



[Plate XIII.] 



IX my previous experiments on the determination of 

 viscosity by the efflux method!, I have always arranged 

 to have the rate of flow of liquid in the capillary tube very 

 small. The kinetic energy correction in the w T ell-known 

 reduction formula was thus always small in comparison with 

 the first term. In the present experiments, however, I have 

 purposely increased this rate of flow in order to test the 

 formula in cases where the kinetic energy correction is much 

 greater. The glischrometer used in these experiments was 

 of the same form as those previously used by me, but 

 the bulbs were larger. It is shown in fig. 1. At a, b, c, 

 and d, platinum wires are inserted, which are almost touching- 

 inside the tubes. The capillary C is fitted to the limbs by 

 rubber bands. The volume of the bulb R at 0° C. is 

 10*2801 ccs., and that of L at the same temperature 

 10*3201 ccs. Four capillaries were carefully selected for 

 separate use in the glischrometer, and their ends were ground 

 with fine emery, in a lathe. Their lengths, measured directly 

 with callipers, were 5*570, 6*494, 5*408, and 6*456 cms. 

 respectively at 0° C, and their radii approximately were 

 •019, -019, -020, -020 cm. respectively, at 0° 0. (The exact 

 determination of the equivalent radius of each capillary was 

 made at the end of all the experiments. It involved the 

 cutting up of the tube and the careful measurement of the 

 sections.) Sufficient freshly distilled water was put in to 

 fill up the glischrometer from b to c. 



* Communicated by the Author. Read before the Royal Society of 

 N. S. Wales, June 3, 1908. 



t Phil. Mag. March 1900; May 1902 ; May 1904. 



