The Total Solar Echpse of 1900. 
Temperature of the Air during the Eclipse. 
87 
With a view to determining the changes in the air temperature during the 
progress of the eclipse, I brought out with me a Richard thermograph of the usual 
pattern, except that the clockwork was so 
modified that a revolution of the drum 
occupied only three hours (instead of a 
week, as in the ordinary type), so as to get 
an open time-scale. This was placed in a 
well-ventilated wooden stand, and shielded 
from the direct radiation of the Sun. A 
good mercurial thermometer, which had 
previously been compared with a standard 
thermometer at the Radcliffe Observatory, 
was suspended in the same stand, with its 
bulb in close proximity to the tube of the 
thermograph. Just before the beginning 
of the eclipse—at 2" 50" G. M. T.—the 
mercurial thermometer was read, and the 
corresponding point of the thermographic 
record marked upon the sheet. A similar 
comparison was made at three subsequent 
epochs, with the following results :— 
G.M.T. Reading. 
As 2? HOF oye B} I 
3 20 82-0 ,, 
4 20 18 °O xp 
4 41 TB °S 5 
From these four points on the curve the 
time and temperatures were subsequently 
determined by Mr. Wickham, the first assist- 
ant at the Radcliffe Observatory, as indicated 
in fig. 7. 
It will be seen from this diagram that 
the change in the temperature of the air, due 
to the coming on of the total phase, was 
not very striking, amounting to only 8°:2. 
The fall in temperature, which was on 
the whole very steady during the partial 
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Fig. 7. 
