168 
DR. M. W. TRAVERS, MR. G. SEXTER, AND DR. A. JAQUEROD 
The following table shows the order of the agreement between the measurements 
of temperatures near the boiling-point. 
Hydrogen Scale. 
Thermometer. 
1 
Observed vapour 
pressures. 
Observed temperature. 
Temperature 
from smoothed cui’A-es. 
o 
o 
A 
757-2 
20-17 
20-21 
B 
766-6 
20-28 
20-2.5 
Helium Scale. 
Thermometer. 
Observed A-apour 
pressures. 
ObserA'ed temperature. 
Temperature 
from smoothed curA'es. 
millims. 
o 
o 
A 
765-0 
20-12 
20-41 
R 
759-2 
20-11 
20-41 
c 
770-0 
20-13 
20-45 
D 
7-19-0 
20 - 36 
20-.36 
With regal’d to the measurements at lower pressures, the greatest difference 
between the observed and calculated temperatures in the tirst series of measurements 
with the helium tliermometer exceeds Od. These errors can lie accounted for by 
supposing that when the liquid liydrogen surrounding the thermometer bub) was 
made to l)oil under reduced pressure, the observations Avere made l)efore the tempera¬ 
ture of the tliermometer bull), and of the bull) containing tlie })ure liquetied hydrogen, 
had Ijecome steady. 
At pressures beloAv 200 millims. it ap 2 )eared to be much more easy to maintain 
a steady temperature than at intermediate pressures. In the last series of measure¬ 
ments, as has already been stated, tAvo bulbs containing pure liquid hydrogen and 
connected Avith tAvo manometers, Avere immersed at different leA-els in the A'acuum 
vessel containing the liquid hydrogen surrounding the thermometer bulb, to the 
depth of the top and of the bottom of the thermometer bulb respectiA*ely. The 
pressures indicated by the manometers Avere read simultaneously and Avere neA'er found 
to differ by more than 1 millim., proving that the temperature of the thermometer 
bulb Avas practically uniform. 
In concluding these remarks on the accuracy of the results, it may be Avell to point 
out that the expression of differences of temperatures in degrees, particularly at Ioav tem- 
])eratures, in degrees, is somewhat a])t to lead to a lalse conclusion. In dealing Avith 
the thermodynamic cycle, on w Inch our idea of an absolute scale of temperature is 
