Onginal Letters of Dr. Franklin. 365 
October storta, which with you was on the 8th, be- 
gan on the 7th in Virginia and N. Carolina, and was most vi- 
olent there. As tothe reason of this, I can only give you 
my conjectures. Suppose a great tract of country, land and 
sea, to wit, Florida and the bay of Mexico, to have clear 
~ weather for several days, and to be heated by the sun, and 
its air thereby exceedingly rarefied : Suppose the country 
north-eastward, as Pennsylvania, New-England, Nova-Sco- 
tia, Newfoundland, &c. to be at the same time covered with 
clouds, and its air chilled and condensed. The rarefied air 
~ being lighter must rise, and the dense air next to it will press 
into its place ; that will be followed by the next denser air, 
that by the next, and soon. ‘Thus when I have a fire in 
my chimney, there is a current of air constantly flowing from 
the door to the chimney : but the beginning of the motion 
was at the chimney, where the air, being rarefied by the fire, 
rising, its place was supplied by the cooler air that was next 
to it, and the place of that by the next, and so on to the door. 
So the water in a long sluice or mill-race, being stopped by 
a gate, is at rest, like the air in a calm; but as soon as you 
open the gate at one’ end to let it out, the water next the 
gate begins first to move, that which is next to it follows; and 
so though the waier proceeds forward to the gate; the mo- 
tion which begun there runs backwards, ifone may so speak, 
to the upper end of the race, where the water is last in mo- 
tion. We have on this continent a long ridge of mountains, 
running from N. East to 5. West; and the coast runs the 
same course. ‘These may, perhaps, contribute towards the 
direction of the winds or atleast influence them in somede- 
gree. If these conjectures do not satisfy you, I wish to have 
yours on the subject. 
1 doubt not but those mountains which you mention con- 
tain valuable mines, which time will discover. I know of 
but one valuable copper mine in this country, which is that 
of Schuyler in the Jersies. This yields good copper, and 
has turned out vast wealth to the owners. I was at it last 
fall; but they were not then at work: the water is grown 
too hard for them, and they waited for a fire engine from 
England to drain their pits. I suppose they will have that 
at work next summer 5 it costs them 1000/: sterling. 
Col. John Schuyler, one of the owners, has a deer park 
five miles round, fenced with cedar logs, five logs high, with 
VouwlV:. No. 2: 21 . 
