Inlelligence and Miscellaneous Articles. 227 



The above are very accurate contemporaneous values of the decli- 

 nation and dip at the three places, and tlie formulae derived from 

 them will probably apply with considerable accuracy to any place 

 in the United Kingdom at any date not very remote from 1843. 

 For the Cambridge observatory V— Vo= -f 3''7 and D— Do = 



The mean result from 24 observations of the position of the 

 corona is, that it was situated 5' further from the astronomical 

 zenith, and 1° 14' nearer to the meridian than the point of the 

 heavens to which the south end of the dipping-needle was directed. 



The places of the corona given by the different observations ex- 

 hibit considerable discrepancies, which are accounted for by saying, 

 that as the formation of the corona is merely an effect of perspective, 

 its position varies, since the streamers are not exactly parallel, with 

 the locality from which they rise ; also with any variation of their 

 direction at a given locality ; and, supposing the course of the 

 streamers to be somewhat curved in their ascent, it will vary with 

 the height to which they rise. Accordingly, as appeared to be the 

 fact, the corona would be continually shifting its position within 

 certain limits. 



Prof. Challis has made a similar comparison with observations of 

 the position of the corona of the same aurora made at Haverhill, at 

 Darlington, and at Bath ; also with observations at Whitehaven of 

 the aurora of Oct. 18, 1848, and of that of Oct. 24, 1847, at Cam- 

 bridge. From a consideration of all the results derived from the 

 discussion of observations made on different occasions and at differ- 

 ent places, the following conclusions seem to be established : — 



First, that the corona of an aurora borealis is formed near the 

 point of the heavens to which the south end of the dipping-needle at 

 the place of observation is directed. 



Secondly, that the observations, while they indicate no decided 

 difference of altitude between the two points, show with great pro- 

 bability that the corona is the more westerly by about l^° measured 

 on an arc perpendicular to the meridian. 



The paper concludes with a particular description of the aurora 

 borealis of Nov. 17 as observed at the Cambridge Observatory, and 

 iVith three tables of the observations of declination, horizontal force, 

 and vertical force, made at Greenwich, and used in the calculations. 

 These observations present so striking an instance of great magnetic 

 disturbances occurring simultaneously with an extraordinary display 

 of the aurora borealis, that the connexion in some way of the two 

 kinds of phaenomena must be regarded as a physical fact. 



XXXII. Intelligence and Miscellafieous Articles. 



ON THE RATIONALE OF THE EXPLOSION CAUSING THE GREAT 

 FIRE OF 1845 AT NEW YORK. BY DR. HARE*. 



T^R. HARE communicated to the meeting some inferences and 

 ■^-^ facts, tending to explain the contradictory impressions which 

 * Communicated by the Author. 

 Q2 



