TRANSACTIONS OF THE SECTIONS. 401 



Communication respecting an Arch of the Aurora Borealis. 

 By R. Potter J Jun.* 



A very luminous arch of an aurora borealis was observed at 

 Edinburgh by Professor Forbes on the evening of the 21st of 

 March 1833. It was observed at Athboy in Ireland by the 

 Earl of Darnley, by Dr. Robinson at Armagh, and also by a 

 correspondent of one of the Carlisle newspapers. 



The observations demonstrate the view of the symmetrical 

 arches being similar to parallels of latitude round the magnetic 

 axis, the arch being seen in those positions at Edinburgh, 

 Armagh, and Athboy which such a direction requires. 



Report of Experiments on the Quantities of Rain falling at dif- 

 ferent Elevations above the Surface of the Ground at York, 

 undertaken at the request of the Association, by William 

 Gray, Jun., awe? John Phillips, F.R.S. G.S., Secretaries of 

 the Yorkshire Philosophical Society ; with Remarks on the 

 Results of these Experiments, % John Phillips, F.R.S. G.S. 



I. Report of the Experiments. — York, the site of these 

 experiments, stands in the centre of perhaps the most uniform 

 and extensive vale in England, reaching from the mouth of the 

 Tees to the aestuary of the Humber, a length of 70 miles, with 

 a breadth of from 15 to 25 miles. In this vast space no ground 

 rises more than 100 or 150 feet above the level of York ; and 

 the Minster, elevated 200 feet from the ground, looks down upon 

 an area of above 1000 square miles, in which hardly any object, 

 whether of nature or art, rises to within 100 feet of its summit. 



On the east the vale is bordered by the range of the Wolds, 

 whose extreme height is 805 feet, and the escarpments of the 

 oolitic system, which swell to 1485 feet. On the west, the 

 distant hilly regions of the coal and limestone tract appear 

 above the low plateau of magnesian limestone. 



These circumstances of situation give an importance to the 

 moderate height of York Minster which is denied to many 

 loftier buildings in England. From its summit the course of a 

 passing storm may be well traced from even the distant hills of 

 Richmond ; and the deflections occasioned by the attraction of 

 the sides of the vale, the rushing of the air, the sudden fall 

 of temperature, and many other curious phaenomena accom- 

 panying the precipitation of rain, may be well observed. 



It is, probably, to the peculiarity of its geographical situation 

 that we are to attribute the remarkable general regularity of the 

 curves of mean temperature at York ; for the deviation of the 



* See Lond. and Edinb. Philosophical Magazine, Third Series, vol. iii. p. 422. 



1833. 2 D 



