BoEDDiCKEE — On Lunar Radiant Heat. 



505 



3. It may be worth while once more to recapitulate the assumptions at 

 variance with the facts which I made in order to simplify the computation. 

 It was assumed that 



a. the diameter of the Moon was 1903.2", instead of 1905.8"; 



b. the diameter of the shadow was 2559.8", instead of 2558.8" ; 



c. the Moon moved uniformly along a semi-diameter of the penumbra ; 



d. the Sun's light was uniform ; 



e. the Moon's light was uniform. 



I do not think that these deviations from reality seriously affect the accuracy 

 of the result as far as our present purpose is concerned. 



4. The values of the lunar heat taken from the final curve (Plates LIII. and LIV.) 

 were next expressed in per cents, of the value of 4**- 9"2"", viz. 658-0, and the two 

 curves (light and heat) were drawn on the same piece of paper with the time as 

 abscissse and the light- and heat-values as ordinates. These curves are reproduced 

 on Plate LV., the quantities on which they are based (to tenths of per cents., and 

 from 5 to 5 minutes only) follow below in tabular form. For the sake of 

 comparison I have added on the same plate and in the same Table the observations 

 made and the light-curve computed in 1884. The time is counted from the 

 middle of the eclipse in each case. It will be seen that I have added hypothetical 

 values during totality, which are simply obtained by connecting in the most 

 probable manner the two observed branches of the heat-curves, and which 

 obviously can only give a somewhat vague idea of the course the curves would 

 have taken had observing been possible. 



In comparing the curves of 1884 and 1888 the difference of the magnitudes of 

 the two eclipses must be borne in mind. I add, therefore, here the necessary 

 data, from which it will be seen that the more recent eclipse lasted 13 minutes 

 longer than its predecessor. 



First contact with penumbra, 

 ,, ,, witli shadow, 



Beginning of totality, 



Middle of eclipse, 



End of totality. 



Last contact with shadow, 

 ,, ,, with penumbra, 



TRANS. EOT. DUB, SOC, N.S. TOL. PV., PAET IX, 



4B 



