322 BeppickEr— On the Changes of the Radiation of Heat from the Moon. 
The sensitiveness attained by this appeared sufficient for the present purpose, 
though it did not come up to that of 1881. This alteration necessitated, obviously, 
lunar heat determinations before and after the eclipse, in order to enable me to 
see whether or not the apparatus underwent any change during the eclipse, and 
also to deduce a satisfactory value for the heat corresponding to full moon, which 
would be necessary for the discussion of the eclipse observations. Such additional 
observations were obtained on October 3, 5, 6; November 2, 28, 30, in 1884: 
and on March 24 and 29 in 1885, and are reproduced further on. 
3. The mode of observing during the eclipse was the same as usual (J. c., 
p. 588). As I had found, however, that when the illuminated phase of the moon 
was very small, the moon’s image could not in the usual way be perceived on the 
small condensing mirrors, the late Mr. Butler, master at the Parsonstown Model 
School, remained in the observing gallery of the telescope, as near the thermo- 
piles as could safely be, while the heat determinations were going on, directing 
the motion of the tube, so as to keep the moon’s image constantly on the small 
condensors. This assistance proved exceedingly valuable, as it enabled me to 
observe till within a very few minutes of the total phase. The observations were 
carried on as much as possible uninterruptedly from 20" 27™, sidereal time, or 11™ 
before the first contact with the shadow, till 1" 55™, sidereal time, or 45™ after the 
last contact with the penumbra. The values up to 21” 11", however, were 
obtained through a moderately dense covering of clouds, and are, therefore, of 
no value for our purpose. - Besides this, four unavoidable interruptions took place. 
The first one from 21" 23™ till 21" 27", when a small, low, misty cloud—the last 
trace of the overcast sky—swept over the moon; the second one from 21” 38” till 
23" 16", or from two minutes before the beginning till three minutes after the 
end of the total phase, as during that time it was impossible to make sure that the 
moon’s image was on the condensing mirrors. It is probable that this was to a 
considerable extent due to the unusual degree of darkness which the moon 
attained during this eclipse, and which has been remarked by numerous observers ; 
but I do not think that the apparatus was sufficiently sensitive to show any effect, 
even if it had been possible to expose it properly to the moon’s rays. The third 
interruption took place from 23" 26™ till 23" 32", during which time I examined 
the small condensors, to see whether they were covered with dew, which the 
exceedingly slow increase of the heat effect after the total phase had led me to 
suspect. My apprehension was, however, happily not verified. The last inter- 
ruption, from 0" 40™ till 0° 49" was owing to the rewinding of the driving clock 
of the telescope. 
4, The following Table contains the eclipse observations only. The necessary 
explanations will be found after the Table :— 
