296 On the PraclkabUUy 



passes out again with some force into the a;ther at the same di- 

 stance from the northern. 



Franklin supjposes, " the electric fire discharged into Hie polar 

 regions from vaporised air raised from the ocean hetween the 

 tropics, accounts for the aurora borea/is; and that it appears 

 first, where it is first in motion ; namely, in the most northern 

 part, though the fire really proceeds northward." Father Bos- 

 covich determined the height of an aurora horefdi^, and found it 

 825 miles. Mr. Bergman, from a mean of thirty compulations, 

 made the average height of the mucra borealis 469 miles; but 

 Euler supposes the height to be 7000 miles ; and Marian al>o 

 assigns to them a very elevated region. Thus discordant and 

 various are the conjectures of philosophers on this matter. 



At all events, in whatever way the suppo&ed connexion maybe 

 between the removal of the ice and these phaenomcna, it " seems 

 not Unfair to infer, that the departure of the itiimense nmuntains 

 and fields of ice, which for so many centuries have covered the 

 arctic seas, may have had some effect in stopping the barrier of 

 the western declination of the needle." But we may as fairly 

 draw the same inference from a similar cause, though probably 

 of much less exlent ; and all we can know, till the whole of the 

 arctic regions are explored, is, the departure of perhaps a very 

 buiall portion only, of " these immense mountains and fields of 

 ice," which had collected in the vicinitt/ of Greenland. What 

 may still remain in the arctic seas we are yet to learn; and con-, 

 cerning which, like every thing else where facts and local expe- 

 rience are wanting, our opinions can only i)e formed on some 

 theory l.u'It on fixed, and generally received principles. 



The fact, however, of the disappearance of some large moun-. 

 tains and fields of ice from pari of the arctic regions being ad- 

 mitted, the writer of the article in question then "inquires whether 

 any, and what advantages, may arise out of an event, which for 

 the first time has occurred, at least to so great an extent, during 

 the last four hundred years ;" and among the objects most in- 

 teresting mentions these : 1st. The influence which the removal 

 of " so large a body of ice may have on our climate," 



On the benefits we should derive from an amelioration of our 

 climate, there can be but one opinion. And that our summer 

 seasons have been colder than usual, in the latter years for in- 

 stance, are from the causes he assigns, few will doubt. But the 

 effect produced may not continue. For though the principal 

 cause of the chillness of our climate, compared with what it ap- 

 pears to have been centuries ago, may be removed for ike pre- 

 sent., yet tbe grand primary cause which produced the ice, whose 

 ppproxiiuation delcrioriated our climate, it is to be presumed, 



will 



