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

By Benjamin Franklin

Page 205

the quill. (Plate IX. fig. 1.) If there
were any motion of air through the tube, it would manifest itself
by its effect on the silk; but if the tube and the air in it are
of the same temperature with the surrounding air, there will be no
such motion, whatever may be the form of the tube, whether crooked
or strait, narrow below and widening upwards, or the contrary; the
air in it will be quiescent. Warm the tube, and you will find, as
long as it continues warm, a constant current of air entering below
and passing up through it, till discharged at the top; because the
warmth of the tube being communicated to the air it contains rarefies
that air and makes it lighter than the air without, which therefore
presses in below, forces it upwards, and follows and takes its place,
and is rarefied in its turn. And, without warming the tube, if you
hold under it a knob of hot iron, the air thereby heated will rise
and fill the tube, going out at its top, and this motion in the
tube will continue as long as the knob remains hot, because the air
entering the tube below is heated and rarefied by passing near and
over that knob.

That this motion is produced merely by the difference of specific
gravity between the fluid within and that without the tube, and not
by any fancied form of the tube itself, may appear by plunging it
into water contained in a glass jar a foot deep, through which such
motion might be seen. The water within and without the tube being
of the same specific gravity, balance each other, and both remain
at rest. But take out the tube, stop its bottom with a finger and
fill it with olive oil, which is lighter than water, then stopping
the top, place it as before, its lower end under water, its top a
very little above. As long as you keep the bottom stopt, the fluids
remain at rest, but the moment it is unstopt, the heavier enters
below, forces up the lighter, and takes its place. And the motion
then ceases, merely because the new fluid cannot be successively made
lighter, as air may be by a warm tube.

In fact, no form of the funnel of a chimney has any share in its
operation or effect respecting smoke, except its height. The longer
the funnel, if erect, the greater its force when filled with heated
and rarefied air, to _draw_ in below and drive up the smoke, if one
may, in

Last Page Next Page

Text Comparison with Autobiography of Benjamin Franklin

Page 4
.
Page 23
There was another bookish lad in the town, John Collins by name, with whom I was intimately acquainted.
Page 24
I had never before seen any of them.
Page 25
My time for these exercises and for reading was at night, after work or before it began in the morning, or on Sundays, when I contrived to be in the printing-house alone, evading as much as I could the common attendance on public worship which my father used to exact of me when I was under his care, and which indeed I still thought a duty, thought I could not, as it seemed to me, afford time to practise it.
Page 39
In this, however, he was mistaken.
Page 44
I used to work him so with my Socratic method, and had trepann'd him so often by questions apparently so distant from any point we had in hand,.
Page 70
My friends lamented my connection with him, but I was to make the best of it.
Page 71
He interested himself for me strongly in that instance, as he did in many others afterward, continuing his patronage till his death.
Page 84
"The time which he recommends for this work is about even or bed-time, that we may conclude the action of the day with the judgment of conscience, making the examination of our conversation an evening song to God.
Page 110
The utility of this institution soon appeared, and many more desiring to be admitted than we thought convenient for one company, they were advised to form another, which was accordingly done; and this went on, one new company being formed after another, till they became so numerous as to include most of the inhabitants who were men of property; and now, at the time of my writing this, tho' upward of fifty years since its establishment, that which I first formed, called the Union Fire Company, still subsists and flourishes, tho' the first members are all deceas'd but myself and one, who is older by a year than I am.
Page 116
My education in New England, where a fast is proclaimed every year, was here of some advantage: I drew.
Page 132
"That the mud, when rak'd up, be not left in heaps to be spread abroad again by the wheels of carriages and trampling of horses, but that the scavengers be provided with bodies of carts, not plac'd high upon wheels, but low upon sliders, with lattice bottoms, which, being cover'd with straw, will retain the mud thrown into them, and permit the water to drain from it, whereby it will become much lighter, water making the greatest part of its weight; these bodies of carts to be plac'd at convenient distances, and the mud brought to them in wheelbarrows; they remaining where plac'd till the mud is drain'd, and then horses brought to draw them away.
Page 139
" I ask'd what terms were to be offer'd the owners of the waggons, and I was desir'd to put on paper the terms that appeared to me necessary.
Page 140
4.
Page 142
Clair, the hussar, with a body of soldiers, will immediately enter the province for the purpose, which I shall be sorry to hear, because I am very sincerely and truly your friend and well-wisher, "B.
Page 148
--_Marg.
Page 154
What made it worse was, that, as soon as we began to move, they drew their swords and rode with them naked all the way.
Page 159
[110] An English baronet (died in 1709), donator of a fund of L100, "in trust for the Royal Society of London for improving natural knowledge.
Page 175
What though you have found no Treasure, nor has any rich Relation left you a Legacy, _Diligence is the Mother of Good-luck_, as _Poor Richard_ says, _and God gives all Things to Industry_.
Page 188
therefore suspected to have received the Contagion; But upon the matter, it doth not appear there was the least Foundation for such a Report; tho' it is too plain the Distemper gains ground space in the Southern Parts of France.