182 Captain Sabine’s experiments to determine the 
with the bobs of the pendulums, and as near them as the extent 
of their arcs of vibration would admit: it is probable, therefore, 
that each thermometer was an index to the variations in tem- 
perature to which the principal part of its pendulum was sub- 
jected; but other thermometers, placed one or two feet higher 
in the clock cases, so far from corresponding, frequently dif- 
fered many degrees from the lower one. Every gradation be- 
tween the temperature of the external air and that of the stove, 
might be remarked at the same time by thermometers placed 
in different parts of the room ; nor was it possible to provide 
against effects which changed with the situation of the sun 
and the direction of the wind. The thermometer was regis- 
tered frequently in the hour, but the result was necessarily 
very unsatisfactory. Moreover, in consequence of the intro- 
duction of the stove into the room, the ground beneath the 
nearest legs of the stand were softened, and the levels af- 
fected, which might not have been the case could the room 
have been sufficiently heated by pipes. 
The mean height of the thermometer in the air during the 
second fortnight in May was between 24 0 and 25 0 ; it is pro- 
bable that the registry of the temperature of the clocks be- 
came then an approximation to the truth ; but this is by no 
means certain, as there was yet very much inequality between 
the heat of the days and of the nights, the latter being still 
very cold ; but the effects of the heat acquired by the land 
were now becoming manifest every where, and advancing 
with great rapidity. 
It was soon found impracticable to keep the levels in any 
thing like adjustment; and by the end of the fortnight, the 
thaw prevailed to such an extent as to oblige the aban- 
