INTENSITY OF SUNLIGHT. 59 



but the average of them makes the light of the sun about 

 jive hundred thousand times as great as that of the full 

 moon on the brightest nights. Of course this can only be 

 considered as an approximate result, as it would be impos- 

 sible, with the means yet devised, to estimate such enor- 

 mous differences of intensity between two lights with 

 much accuracy. 



