[ 287 ] 



XLVII. On Azimuthai Refraction, 

 ^ ToMr.Tillocli, 



Sir, idAViNG recently directed my attention to the sub- 

 ject of retraction in azimuth, and having mentioned the 

 subject to Mr. Williams, ofWells (at piesent residing in 

 Islington), I have received the following letter, stating 

 phasnomena observed by hinj on the 28th ult. depending 

 on aziinuihal as well as vertical refraction. Similar effects 

 were observed on the same day in the north environs of 

 London, by Messrs. Whites of Finsbury-square, and my- 

 self ; but being at that time in the prosecution of other in- 

 quiries, we could not attend particularly to the subject. 

 Mr. W. however, between one and three o'clock, observed 

 three sets of angles (in which the churches of St. Paul, 

 St. Mary Islington, Hampstead, and Stoke Newingtoa 

 formed principal objects), without having any reason to 

 suspect error arising from azimuthai refraction, the fog by 

 this time being more uniformly dispersed, forming a general 

 haziness in the horizon, but not reaching so high as the 

 tops of the above spires. 



I am, sir, 



Your obedient ser\''ant, 



26, Garlick HIU, March 10, 1810, Jos. StEKVENS. 



Mr, Steeveiis, — Sir, 



Although I stated to you at our last interview, that in a 

 very great number of observations, (probably a hundred,) 

 made on Harrow, Hampstead, and another church lying 

 S. W. of Primrose Hill, distance about four miles, I co^ld 

 discover no azimuthai refraction as you term it ; yet I have 

 since, viz. on Fast-day, observed it twice in a very striking 

 manner,- and must do you the justice, before I quit towri, 

 to say I am quite satisfied as to the fact. 



On tlic above day about nine A.M., in my way to Kil- 

 burn crossing some high fields to the south of Primrose 

 Hill, I observed, from the interposition^ of the fog, that se- 

 veral ol)jects put on a strange distorted appearance, and 

 that the spire of Islington church appeared crooked (see 

 Jirist aj)pearance^ PI. VI 1) ; and in less than a minute, about 

 20 fett ot the upper part appeared insulated and not imme- 

 diately over the under part, but as in the margin. (See 

 second appearance,) 



I immediately screwed my telescope into the post of a 



fence which was near me ; but before I could adjust it, the 



• ' , spire 



