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^currents of air, one of them uuder the other. Now 

 as the air between the tropics is rarefied by the SUB, it 

 rises : the denser air is pressed into its place. The air 

 so raised, moves north and south, and if it has no op- 

 portunity before, must descend in the polar regions. 

 When this air with its vapours descends into contact 

 with the vapours arising there, the electric fire which it 

 brought begins to be communicated, and is seen in clear 

 nights; being first visible where it is first in motion, 

 namely in the most northern parts. But from thence 

 the streams of light seem to shoot southerly, even to the 

 zenith of northern countries. 



To the same principle we may refer what some term 

 St. Helmo's fire, and the ancient's, Castor and Pollux, a 

 thin shining light, which is sometimes seen dancing on 

 the decks, or raging of ships. A very remarkable ac- 

 count of this, is given by a late author. " In the night 

 it became exceeding dark, and thundered and lightened 

 dreadfully. We saw mean time on different parts of 

 the ship, above thirty St. Helmo's fires. One which was 

 on the top of the vane of the main mast, was more than 

 a foot and a half in length. I ordered one of the sail- 

 ors to take down the vane : the noise of the fire resem- 

 bled that of fired wet gunpowder. Scarce had he low- 

 ered the vane, but the fire left it, and fixed on the top 

 of the main mast : after remaining there a considerable 

 time, it went out by little and little. 



" How immense a quantity of electric matter must have 

 been at that time in the atmosphere surrounding the ship, 

 to furnish more than thirty St. Helmo's fires, (the same 

 \ve see at the end of our conductors in electrifying) one of 

 which was above a foot and a half long 1 The masts, 

 yards, and every part of the ship were then real con- 

 ductors of the electric fire between the atmosphere 

 and the sea, and by that means preserved the ship." 



A person electrified acquires a flammific power, strong 

 -enough to light with one of his fingers, or with his cane, 

 warm brandy. When the finger draws near, a cracking 

 sparkle issues out, and, sets it on fire. 



