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XXVI. 
NOTES ON TEMPERATURE OBSERVATIONS MADE AT 
DUNSINK OBSERVATORY DURING THE ECLIPSE OF 
THE SUN ON MAY 28, 1900. By C. MARTIN. 
(Puate XXI.) 
[Read Junz 20; Received for Publication Junn 22 ; Published Octozrr 17, 1900.] 
OpsERVATIONS of temperature were made at Dunsink Observatory 
during the recent eclipse of the Sun. The observations were taken 
with two heat radiation thermometers, one with a black bulb, and 
the other with a white bulb, kindly lent to the Observatory by 
Professor Fitz Gerald. These thermometers were mounted about 
an inch apart on a post a little over six feet high. The post was 
painted black, the bulbs of the thermometers being 6 inches away 
from any part of the woodwork, and pointed directly towards the 
Sun. 
It was intended at first to take readings every fifteen minutes, 
but owing to clouds the readings were sometimes made oftener. 
Observations were started at 1.45; but from that time till 2.30 
there were a good many clouds about which obscured the Sun 
every few minutes, so the readings at that time are not of much 
value; but from 2.45 to the time the observations were discontinued 
at 4.45, the Sun was free from clouds, and the observations seem 
very good. From the curves drawn (see Plate XXI.), it will be seen 
that about eight minutes after the middle of the eclipse the tempe- 
rature was at its lowest, and began to rise rapidly as the portion of 
the Sun eclipsed became less. It will also be noticed that as the Sun 
became more eclipsed the temperature fell quickly. The highest 
reading before the eclipse began was 63°-7, and the lowest 35°-7, 
showing a drop of 28° with the black bulb thermometer ; with the 
white bulb the highest reading was 15°-6, and the lowest 8°, 
showing a drop of 12°-6. 
Experiment was made by shading the thermometers to find how 
they were affected. It was found that on an average the black bulb 
