[ 4 ° 3 ] 
u cepted the warmth of the earth from afcending 
u from greater depths below them ; for the fnow lay 
ct where the drain had more than four feet depth of 
te earth over it. It continued alfo to lie on thatch, 
<e tiles, and die tops of walls.’' 
That the air neared: the earth will be mod: warmed 
by the heat of it, is obvious ; and this has frequently 
been taken notice of in the morning, before day, by 
means of thermometers at different diftances from 
the ground, by the reverend Dr. Miles, at Tooting in 
Surrey; and is mentioned in p. fz 6 , of the 48th vo- 
lume of the Philofophical Tranfadtions. 
The aurora borealis, which happens at the time 
the needle is difturbed by the heat of the earth, is 
fuppofed to be the eledtricity of the heated air above 
it ; and this will appear chiefly in the northern re- 
gions, as the alteration in the heat of the air in thofe 
parts will be greatefl. This hypothecs will not feem 
improbable, if it be confidered, that eledtricity is now 
known to be the caufe of thunder and lightning ; that 
it has been extradted from the air at the time of an 
aurora borealis ; that the inhabitants of the northern 
countries obferve the aurora to be remarkably ftrong, 
when a fudden thaw happens after fevere cold wea- 
ther.; and that the curious in thefe matters, are now 
acquainted with a fubftance, that will, without fric- 
tion, both emit and abforb the eledtrical fluid, only 
by the increafe, or diminution of its heat : for if the 
‘Tourmalin be placed on a plane piece of heated glafs, 
or metal, fo that each fide of it, by being perpendi- 
cular to the furface of the heating body, may be 
equally heated; it will, while heating, have the elec- 
tricity of one of its fides pofitive, and that of the other 
F f f 1 nega- 
