( 878 ) 
TABLE ILI. 
Series Il. Brass valve A Air at 0°C. 12/12/07 
(p.—1) ti i 
4.8 warming. 
Oe, + 0.34° C. 
14.5 + 1.04 ,, 
19.4 + 1.72. ,, 
24.2 4253 ,, 
29.0 +335 „ 
Hence, increasing the flow of the gas gave increased cooling effects. 
Further experiments showed that this was so only up to a certain 
point; at a given pressure difference the cooling effect observed as 
the valve opening increased soon attained a maximum and diminished 
as the valve reached its maximum opening; but this was due to the 
fall of pressure along the spiral, to which further reference will be 
made in § 9. 
The assumption that the irregularity observed is due to heat conduction 
obtains further support from these experiments, for heat conduction for 
a given temperature difference between the compressed and expanded 
gas is constant, while the quantity of cooled gas depends, for a given 
pressure, upon the opening of the valve. 
no 
$ 7. At first it was thought that the conduction of heat was due 
to the construction of the valve, which was such that the expanded 
jet had to pass for a short distance along the brass walls of the 
valve immediately after its formation (see fig. 1). A second valve 5 
was then constructed so that the contact of the expanded jet with 
the material of which the valve was made was reduced to a minimum. 
Further series of measurements were made with this new valve, but 
there was no improvement in the results. As before, warming was 
observed at the lower pressures, and, on opening the valve wider, the 
cooling observed at any given pressure increased, reached a maximum, 
and then diminished. The following are the maximum values: 
TABLE III. 
Series V. Brass valve B. Air at 0°C. 18/2/08. 
(p,—1) Tet: 
3.9 atm. warming. 
lien “inversion” 
10 + 0.67° C. 
LOA ras + 1.58 „ 
PAE Marte + 2.84 ,, 
BAO 880 
