288 On Azimiithal Rcfractkiu 



spire became indistinct, being now wholly enveloped in the 

 foe;. I now directed the telescope to llamjistead (Harrow 

 beTncr invisible), the upper part of wliicb was tolerably di- 

 stinct, ahhougii there was a tliick fog at the bottom of the 

 hill. As soon as I had a tolerably good intersection, I 

 quitted hold of the telescope, and found it remarkably 

 steady, it being quite calm ; f soon observed the tower to 

 increase in its height, and shortly after the upper part ap- 

 peared separated from the lower; the lower part retiring a 

 little to the left, while the upper part v/as stationary in 

 azimuth, but increased in altitude; in three or four minutes 

 the top was considerably elevated, but still coincided with 

 the vertical wire, and began to become indistinct as if 

 rising into a cloud ; but before it was quite obscured, I 

 thought I discovered it to be a little to the left of the wire ; 

 the bottom part was now hazy, and still more to the left, 

 apparently about ^ of the whole diameter of the tower; in 

 which situation it disappeared. 



Islington spire was now just visible: it appeared upright, 

 but as far as I could judge by intervening objects was much 

 elevated. The telescope remained unaltered until the fog 

 sufficiently cleared up for further observation on Hamp- 

 stead, which was near three-quarters of an hour, i now 

 found the top and bottom joined, and nearly in the same 

 situation where the bottom ai:)peared just before its obscu- 

 ration, viz. considerably to the left of the wire, where it 

 remained until the telescope was removed It would thence 

 appear, that when I first made the intersection the tower 

 had acquired its greatest elongation, and perhaps might 

 even then have been on its return. 



1 learnt from a gentleman in the course of the day, that 

 one end of a row of houses near Holloway appeared to him 

 first much higher and afterwards much lower than the 

 other, although he did not change his situation : — and 

 from another, that the top of Primrose Hill, with some per- 

 sons on it, appeared to him separated from the bottom and 

 floating in the air, and that he had seen a similar efiect on 

 Qther hills several times before. 



I am, sir, 



Your obedient servant, 



Vpper Street, Idiugto% , ClIARLES WlLLIAM^S. 



March 5, 1810, 



XLVIII. Second 



