► 



On the Fhcenomena of the HoUzontal Moo7i. 67 



irt the meridian; for, in order to divide the space between 

 it and the eye, we need only to look at it behind a cluster 

 of chimneys, the ridge of a hill, or the top of a house," &c. 

 He further observes, " that when the height of all the in- 

 termediate objects is cut off, by looking tlirough a tube the 

 imagination is not helped, and yet the moon seems still as 

 large as before." 



Dr. Smith savs in his Optics, vol. ii. p. 55, of the Re- 

 marks, that in Berkeley's Essay towards a New Theory of 

 Vision* there is the following solution : 



*' Between the eye and the moon, when situated in the 

 horizon, there lies a far greater quantity of atnjosphere than 

 there does when the moon is in the meridian. Whence it 

 comes to pass that the appearance of the horizontal moon 

 is fainter ; and therefore, by sect. 56, it should be thought 

 bigger in that situation than in the nieridiali, or in any other 

 elevation above the horizon." 



" But," says Dr. Smith, " to avoid entering into a par- 

 ticular consideration of his argumenis, 1 choose to show, 

 from experience only, that these various degrees of the 

 moon's faintness make no sensible variation of her apparent 

 magnitude; which, I think, will be evident by the following 

 observations : 



'^ First, that the moon appears much fainter in the day- 

 time than in the night, and therefore, according to our aur 

 thor's principle, should appear larger ; which I could never 

 perceive, though I have often viewed the moon for this pur- 

 pose. 



*' Secondly, I observe that the moon when totally eclipsed 

 appears much fainter than she does at the same elevation 

 when not eclipsed, but does not appear larger than usual, 

 as I am fully satisfied by the total eclipse of the moon on 

 Nov. 20, 1732. 



'^ Lastly, I observe that this hypothesis of faintness can 

 scarce be thought sufficient, by any means, to account for 

 the like variety of the apparent magnitudes of the constella- 

 tions ; that is, of the intervals of the same, fixt stars at va- 



* Piibli^lied in 1709. 



E 2 rioiis 



