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X On the Thermal Conductivity of Water. 
By J. T. Bottomley. 
Communicated by Sir William Thomson, LL.D., F.R.S., Professor of Natural 
Philosophy in the University of Glasgow. 
Received March 11,—Read April 3, 1879. 
The experiments on the thermal conductivity of water, of which an account is given 
in the following paper, were undertaken at the wish of Sir William Thomson, and 
by a method devised by him some years ago. They have been carried out in several 
successive Winter Sessions in the Physical Laboratory of the University of Glasgow, 
with the assistance of students and experimental scholars, among whom I must 
mention specially Mr. J. Beid, Jun., and Mr. M. T. Brown. 
Description of apparatus. —Figs. 1 and 2 show the arrangement of apparatus for 
experiments on the thermal conductivity of a liquid. In each case I have a vessel or 
tank so large that the heat lost at the sides does not affect sensibly the condition of 
the central portion of the liquid, either directly, or by convection currents set up close 
to the sides. The water or other liquid to be experimented on is contained in this 
vessel and is heated from above. 
The tank, fig. 1, is a cylindrical vessel of thin sheet iron. It is 120 centims. in 
diameter and 60 centims. high. At the top there is a hollow cover in contact with 
the water in the tank, and a current of steam is kept blowing through this hollow 
cover. The steam enters by the pipe a and is blown out by the pipe b, which is made 
to dip down to the bottom of the steam chamber in such a way that the water formed 
in the chamber by the condensation of the steam is blown out through this pipe along 
with the surplus steam. In the middle of the hollow cover, or steam chamber, there 
is a rectangular opening, walled in so as to make the chamber steam-tight, and the 
stems of the thermometers employed in the experiments pass up through this opening. 
The water being heated from above transmits the heat downward to the layers beneath. 
The tank shown in fig. 2 is a wooden vessel, an ordinary wine cask, about 64 centims. 
in diameter, and 90 centims. high. It had the disadvantage of not being uniform in 
section from top to bottom, but this had been done away with in tanks recently con¬ 
structed. I require a wooden vessel for experimenting on solutions of salts in water. 
Solution of sulphate of zinc, for example, quickly corrodes and eats its way through an 
iron vessel; and solution of sulphate of copper (at any rate solution of the sulphate of 
capper of commerce) eats through both iron and copper. 
