ASTRONOMY AXD METEOROLOGY. 383 



The next step was to compare, in precisely the same way, the 

 image of the moon reflected from the silvered globe with a Bengola 

 light of the same size and manufacture. This was done at a time 

 when the moon was nearly full and the sky perfectly clear. 



Applying to the respective results thus obtained the necessary cor- 

 rections (i. e., for atmospheric extinction of light, etc.), Mr. Bond 

 found the average light of the sun to be four hundred and seventy- 

 one thousand (470,980) times brighter than the mean full moon. 



The following table also shows the relative intensity of sunlight 

 and that of other celestial objects, as determined by Mr. Bond : 



Sunlight = 470,980 times the light of the mean full Moon. 



" = 622,000,000 " " Venus at maximum brilliancy. 



" = 3,028,350,000 " " " Jupiter at mean opposition. 



" = 5,970,500,000 " " " Sirius. 



" = 18,924,000,000 " " " Alpha Centauri. 



= 24,946,500,000 " " " Alpha Lyrae. 



* = 25,586,500,000 " " " Rigef. 



= 52,001,000,000 " " Spica. 



The average light of the full moon, according to Mr. Bond, is six 

 thousand four hundred and thirty (6430) times greater than that of 

 Jupiter seen from the earth at its mean opposition ; while Venus, at its 

 greatest brilliancy, is nearly five (4864) times brighter than Jupiter. 



Experiments for determining the ratio of sunlight to moonlight, as 

 regards their chemical intensities, give a ratio of three hundred and 

 forty thousand to one. 



Observations on the Light of the Moon and of the Planet Jupiter. 

 In endeavoring to photograph the planet Jupiter on plates exposed at 

 the focus of the great refracting telescope of the observatory of Cam- 

 bridge, Mr. Bond has found that it (Jupiter) reflects, out of a given 

 quantity of incident light, fourteen times more of the chemical rays 

 than the moon does ; or, in other words, the latter, if the constitution 

 of its surface resembled that of Jupiter, would photograph in one- 

 fourteenth of the time it actually requires ; whereas it was to have 

 been expected, considering the relative distances of the two bodies 

 from the sun, that the light of the moon would have had twenty- 

 seven times more chemical intensity than that of Jupiter, supposing 

 equal capacities for reflection. M. De la Rue, of England, noticed, 

 in 1859, that the chemical rays from Jupiter were twelve times more 

 energetic than those from Saturn, a result not wholly attributable, in 

 his opinion, to the circumstance of the greater distance of Saturn. 



No sufficient explanation of the superior chemical energy of the 

 light of Jupiter can be given. The whiteness, or albedo, of the sur- 

 face of Jupiter exceeds that of the moon, says Mr. Bond, in the pro- 

 portion of eleven or twelve to one ; while the moon bears in this 

 quality a general resemblance to the earth. No opaque substance 

 has been found of a whiteness comparable to the bright belts of Jupi- 

 ter, or which under similar illumination will shine with the same 

 intensity. 



Mr. Bond also notices the changes in the intensity of moonlight 



^j * <^ 



at the several phases of our satellite. The brightness somewhat sud- 

 denly increases when it approaches opposition, as though a greater 

 number of the reflecting facets of its asperities were disposed in such 

 a manner as to reflect fight with the greatest advantage ; the effect 



