between the viscosity of liquids and their chemioal nature. 425 
limb, by causing a small quantity to pass through the capillary tube, the temperature 
was obtained at which the quantity of liquid introduced into the glischrometer 
exactly filled it up to the marks, all the observations being made through the reading 
telescopes. The glischrometer was next withdrawn from the batli, its open ends 
closed hy india-rubber caps, and allowed to take up the temperature of the balance 
case; the caps were then removed and the weight ascertained. Knowing the weight 
of the glischrometer alone, the weight of water (reduced to a vacuum) which at the 
temperature of the water-bath filled the instrument up to the marks could be ascer¬ 
tained, and on introducing corrections for the expansion of the water and of the 
glass, the volume at 0° could be readily calculated. 
From two concordant sets of observations carried out in this way the mean volumes 
were found to be 
Right limb, 2'6731 cub. centims. 
Left limb, m}, m^, 2*5513 ,, 
The amount of liquid which in any observation flows through the capillary tube is, 
of course, less than either of the above volumes by the quantity which adheres to the 
wall of the glischrometer-limb between the upper and lower marks. To obtain some 
idea of the amount thus adhering, a glass vessel was made of as nearly as possible tlie 
same shape and size as a limb of the glischrometer. This vessel was fixed vertically, 
filled with water, and the amounts which at ordinary temperatures adhered to the 
sides when the times taken by the water to flow from the vessel were about the same 
as that of the actual viscosity observations were determined by weighing. About 
*002 grm. was found to adhere, and with rise in temperature the amount appeared to 
diminish. The error thus introduced in the case of water corresponds to 1 in 1300, 
and is within the limits of the accuracy to which we could attain. 
Dimensions of the Capillary Tube .—It was expected, and it so happened, that several 
tubes would be brokeii before one was successfully sealed into the glischrometer in the 
manner already described. On this account measurements of the mean diameter 
and length of the capillary were deferred till the sealing in had been accomplished. 
Having ascertained, by rough optical measurements, that the section of the bore of 
a piece of capillary tubing was nearly circular, and that its mean diameter was suit¬ 
able, before cutting off the required length, the tubing was marked as shown. BC being 
Bi B 
B 
B. B, 
the length required, at these points two cuts were made with a sharp file, and on either 
side of each cut, the same letter, or Bg, was etched on the tube with glass-ink. The 
length, BC, was then broken off, carefully protected from dust, and sent to the glass- 
blower. Optical measurements made on the section of the pieces AB and CD at their 
MDCCCXCIV.—A. 3 I 
