544 
MR. J. T. BOTTOMLEY ON THE 
Table II.—Results of experiments on thermal conductivity of water, expressed 
in square centimetres per second. 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
1873, 
Date and hour of experiment. 
Results. 
Dec. 3, 1 p.h. to 2 p.m. . . , 
,, 9, 10.15 a.m. to 11.15 a. it. 
•00209 
•00276 
, ,, „ 11.20 a.m. to 12.20 p.m, 
, ,, „ 12.25 p.m. to 1.25 p.m. 
, ,, ,, 1.30 p.m. to 2.30 p.m. 
1873, Dec. 10, 11 a.m. to 12 noon . 
„ ,, ,, 12 noon to 1 p.m. . 
„ ,, „ 1.30 p.m. to 2.30 p.m. 
,, ,, ,, 2.30 p.m. to 3.30 p.m. 
■00226 
•00212 
•00230 
•00235 
•00230 
•00236 
•00228 
•00244 
•00218 
•00229 
•00231 
1876, March 24, 2 p.m. to 3 p.m. . . 
„ ,, ,, 3 p.m. to 4 p.m. . . 
,, „ 31, 1.40 p.m. to 2.40 p.m. 
•00197 
•00212 - 
•00194 
Remarks. 
Beating commenced always abont 9 a . m . 
Results 1-13 obtained by method of fig. 1. 
Probably too high a result owing to some dis¬ 
turbance at the beginning of the experiment. 
Other results calculated from observations of 
December 9 th taking different intervals of time 
during the experiment. 
Results 14-16 obtained by method of fig. 2. 
The results given by this method have uni¬ 
formly given a smaller number for the conduc¬ 
tivity than that given by the first method. I 
attribute this to one or both of two causes. 
First, the supply of beat is limited and is not 
large enough in the arrangements that I bad 
at my command when these experiments were 
made, and, secondly, the vessel in which the 
experiments were made was not, I believe, 
large enough to make sure of no loss by the 
sides. Some experiments that I made in a 
much smaller vessel some time ago pointed 
clearly to this cause, giving me a very low 
number for the value of Jc. I hope with im¬ 
proved apparatus to make sure of the result; 
but in the meantime I believe it to be about 
0'002 of a square centimetre per second. 
Additional Note. 
(Added December, 1880.) 
In the foregoing paper I have supposed that by taking a vessel of very large 
horizontal cross section I should be able to eliminate the sensible effect of conduction 
of heat downwards by the sides of the vessel. However, considering the importance 
of the part which the sides might play, and the statements in books and published 
writings that the conduction of heat downwards in liquids, observed by Depretz and 
others, was wholly, or nearly wholly, due to conduction by the sides of the containing 
vessel, it was considered advisable to put the matter to direct test. The following 
experiments were accordingly made at the suggestion of Professor Stokes in the 
months of March and April last. 
In order to test any possible effect producible by the conduction ot heat downwards 
