The Complete Works in Philosophy, Politics and Morals of the late Dr. Benjamin Franklin, Vol. 2 [of 3]

By Benjamin Franklin

Page 204

to the bottom of a decanter
half filled with cold water; then putting a rag over the bowl, blow
through it and make the smoke descend in the stem of the pipe, from
the end of which it will rise in bubbles through the water; and being
thus cooled, will not afterwards rise to go out through the neck of
the decanter, but remain spreading itself and resting on the surface
of the water. This shows that smoke is really heavier than air, and
that it is carried upwards only when attached to, or acted upon, by
air that is heated, and thereby rarefied and rendered specifically
lighter than the air in its neighbourhood.

Smoke being rarely seen but in company with heated air, and its
upward motion being visible, though that of the rarefied air that
drives it is not so, has naturally given rise to the error.

I need not explain to you, my learned friend, what is meant by
rarefied air; but if you make the public use you propose of this
letter, it may fall into the hands of some who are unacquainted with
the term and with the thing. These then may be told, that air is a
fluid which has weight as well as others, though about eight hundred
times lighter than water. That heat makes the particles of air recede
from each other and take up more space, so that the same weight of
air heated will have more bulk, than equal weights of cold air which
may surround it, and in that case must rise, being forced upwards by
such colder and heavier air, which presses to get under it and take
its place. That air is so rarefied or expanded by heat may be proved
to their comprehension, by a lank blown bladder, which, laid before a
fire, will soon swell, grow tight and burst.

[Illustration: (remedies for smoky chimnies)

_Plate IX._ _Vol. II. page 269._

_Published as the Act directs, April 1, 1806, by Longman, Hurst, Rees
& Orme, Paternoster Row._]

Another experiment may be to take a glass tube about an inch in
diameter, and twelve inches long, open at both ends and fixed upright
on legs, so that it need not be handled, for the hands might warm it.
At the end of a quill fasten five or six inches of the finest light
filament of silk, so that it may be held either above the upper
end of the tube or under the lower end, your warm hand being at a
distance by the length of

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

Page 0
BENJAMIN FRANKLIN, AND Communicated in several Letters to Mr.
Page 1
Animals are in an Instant struck breathless, bodies almost impervious by any force yet known, are perforated, and metals fused by it, in a moment.
Page 3
when you form a direct communication as above.
Page 4
Touch the top first, and on approaching the bottom with the other end, you have a constant stream of fire, from the wire entering the bottle.
Page 5
Page 7
By candle light, even tho' the candle is at a foot distance: these do it suddenly.
Page 8
Of the disposition and application of which wheels, and the various phaenomena resulting, I could, if I had time, fill you a sheet.
Page 13
So a strait spring (tho' the comparison does not agree in every particular) when forcibly bent, must, to restore itself, contract that side which in the bending was extended, and extend that which was contracted; if either of these two operations be hindered, the other cannot be done.
Page 18
Page 19
As the glass is thickest near the orifice, I suppose the lower half, which being gilt was electrified, and gave the shock, did not exceed two grains; for it appeared, when broke, much thinner than the upper half.
Page 20
allowing (for the reasons before given, s 8, 9, 10,) that there is no more electrical fire in a bottle after charging, than before, how great must be the quantity in this small portion of glass! It seems as if it were of its very substance and essence.
Page 21
Water being electrified, the vapours arising from it will be equally electrified; and floating in the air, in the form of clouds, or otherwise, will retain that quantity of electrical fire, till they meet with other clouds or bodies not so much electrified, and then will communicate as beforementioned.
Page 22
Thus the whirling glass globe, during its friction against the cushion, draws fire from the cushion, the cushion is supplied from the frame of the machine, that from the floor on which it stands.
Page 27
motion, and leaping from body to body, or from particle to particle thro' the air.
Page 28
If they are different things, yet they may and do subsist together in the same body.
Page 31
Apply the wire of a well-charged vial, held in your hand, to one of them (A) Fig.
Page 33
has the line A, E, for its basis.
Page 35
And if the person holding the point stands upon wax, he will be electrified by receiving the fire at that distance.
Page 41
a right angle, the two next obtuse angles, and the lowest a very acute one; and bring this on your plate under the electrified plate, in such a manner as that the right-angled part may be first raised (which is done by covering the acute part with the hollow of your hand) and you will see this leaf take place much nearer to the upper than to the under plate; because, without being nearer, it cannot receive so fast at its right-angled point, as it can discharge at its acute one.
Page 49
I have also smelt the electrical fire when drawn through gold, silver, copper, lead, iron, wood, and the human body, and could perceive no difference; the odour is always the same where the spark does not burn what it strikes; and therefore I imagine it does not take that smell from any quality of the bodies it passes through.