3 
1909-10.] Andrews’ Measurements of Compression. 
space, and shows at a glance the relation of the numbers now tabulated 
to those given by Andrews himself in his great memoirs. 
Professor Tait intended to reproduce only the data of the results given 
in the first memoir, the Bakerian Lecture of 1869 ; but the much more 
compact tabulation now adopted makes it possible to treat similarly the 
Bakerian Lecture of 1876, and also the posthumous paper in continuation 
of the same great subject, the manuscript of which was found among 
Dr Andrews’ papers and was transmitted in 1886 by Professor Tait to 
Sir George Stokes for publication in the Philosophical Transactions. On 
page 52 of that last memoir, reference is made to experiments with a 
mixture of 6*2 volumes of carbonic acid and 1 volume nitrogen. The data 
for these experiments, which are fully recorded in the notebooks, have 
been added for the sake of completeness. 
Each series of experiments began with a careful calibration of the 
tubes used ; and to facilitate the calculation of the volumes of the fluids 
compressed, Dr Andrews prepared very full tables from which the required 
values were got by mere inspection. The entries from these tables made 
by Andrews himself have been checked in every case, and once or twice 
a slight error in the last figure was detected. This was, however, just 
within the errors of observation. 
The tabulation is made on the same principle throughout. There are, 
in general, ten columns of figures. The first column gives the number 
attached to the experiment in the notebook, and at the head of the column 
the corresponding notebook and volume in which it is bound are named. 
The second column gives the position of the experiment in the corre- 
sponding table published in the Bakerian Lectures and the posthumous 
memoir. The third, fourth, and fifth columns give the temperature, length 
of the air (or hydrogen) column, and the corresponding volume in cubic 
centimetres. The seventh, eighth, and ninth columns contain the same 
quantities for the carbon-dioxide (or the mixture) ; and the tenth gives the 
difference of level between the mercury surfaces in the two tubes. The 
sixth column is reserved for the real pressures to which the carbon 
dioxide is subjected. To get each true pressure we first estimate the 
pressure of the manometric gas (air or hydrogen, as the case may be) from 
the given values of the volume and temperature, and then apply the 
correction for the difference of level of the mercury surfaces in the two 
tubes, positive or negative, according as the surface in the tube containing 
the carbon dioxide stands lower or higher than the other. 
On page 580 of the Bakerian Lecture of 1869 (pp. 303-4 of the 
Scientific Papers) Dr Andrews shows how the results were calculated by 
