Memoirs of Benjamin Franklin; Written by Himself. [Vol. 2 of 2] With his Most Interesting Essays, Letters, and Miscellaneous Writings; Familiar, Moral, Political, Economical, and Philosophical, Selected with Care from All His Published Productions, and Comprising Whatever Is Most Entertaining and Valuable to the General Reader

By Benjamin Franklin

Page 177

Philosophical Society,
November 22, 1782.

Passy, September 22, 1782.

I return the papers with some corrections. I did not find coal mines
under the calcareous rocks in Derbyshire. I only remarked, that at the
lowest part of that rocky mountain which was in sight, there were oyster
shells mixed in the stone; and part of the high county of Derby being
probably as much above the level of the sea as the coal mines of
Whitehaven were below it, seemed a proof that there had been a great
_boulversement_ in the surface of that island, some part of it having
been depressed under the sea, and other parts, which had been under it,
being raised above it. Such changes in the superficial parts of the
globe seemed to me unlikely to happen if the earth were solid to the
centre. I therefore imagined that the internal parts might be a fluid
more dense, and of greater specific gravity than any of the solids we
are acquainted with, which therefore might swim in or upon that fluid.
Thus the surface of the globe would be a shell, capable of being broken
or disordered by the violent movements of the fluid on which it rested.
And as air has been compressed by art so as to be twice as dense as
water, in which case, if such air and water could be contained in a
strong glass vessel, the air would be seen to take the lowest place, and
the water to float above and upon it; and as we know not yet the degree
of density to which air may be compressed, and M. Amontons calculated
that its density increasing as it approached the centre in the same
proportion as above the surface, it would, at the depth of---- leagues,
be heavier than gold; possibly the dense fluid occupying the internal
parts of the globe might be air compressed. And as the force of
expansion in dense air, when heated, is in proportion to its density,
this central air might afford another agent to move the surface, as well
as be of use in keeping alive the subterraneous fires; though, as you
observe, the sudden rarefaction of water coming into contact without
those fires, may also be an agent sufficiently strong for that purpose,
when acting between the

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Text Comparison with Experiments and Observations on Electricity Made at Philadelphia in America

Page 2
At the same time that the wire and top of the bottle, &c.
Page 4
2.
Page 7
--Or fix a needle to the end of a suspended gun-barrel, or iron rod, so as to point beyond it like a little bayonet; and while it remains there, the gun-barrel, or rod, cannot by applying the tube to the other end be electrised so as to give a spark, the fire continually running out silently at the point.
Page 10
As the vessel is just upon sailing, I cannot give you so large an account of American Electricity as I intended: I shall only mention a few particulars more.
Page 16
20.
Page 21
Non-electric bodies, that have electric fire thrown into them, will retain it 'till other non-electrics, that have less, approach; and then 'tis communicated by a snap, and becomes equally divided.
Page 23
If the particles of water bring electrical fire when they attach themselves to air, the repulsion between the particles of water electrified, joins with the natural repulsion of the air, to force its particles to a greater distance, whereby the triangles are dilated, and the air rises, carrying up with it the water.
Page 26
The air so rarified and forced up, passes northward and southward, and must descend in the polar regions, if it has no opportunity before, that the circulation may be carried on.
Page 27
This is supposed to account for the _Aurora Borealis_.
Page 28
53.
Page 31
'Tis supposed they form triangles, whose sides shorten as their number increases; 'till the common matter has drawn in so many, that its whole power of compressing those triangles by attraction, is equal to their whole power of expanding themselves by repulsion; and then will such piece of matter receive no more.
Page 34
19.
Page 35
Let it be charged, and then present the point at the same distance, and it will suddenly be discharged.
Page 38
If one strip of gold, the length of the leaf, be not long enough for the glass, add another to the end of it, so that you may have a little part hanging out loose at each end of the glass.
Page 39
And though I have taken up the pieces of glass between my fingers immediately after this melting, I never could perceive the least warmth in them.
Page 41
By a little practice in blunting or sharpening the heads or tails of these figures, you may make them take place as desired, nearer, or farther from the electrified plate.
Page 42
I know it is commonly thought that it easily pervades glass, and the experiment of a feather suspended by a thread in a bottle hermetically sealed, yet moved by bringing a nibbed tube near the outside of the bottle, is alledged to prove it.
Page 43
[Illustration] 33.
Page 51
_Windmil wheels_, &c.
Page 54
[9] See s 10 of _Farther Experiments_, &c.