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

By Benjamin Franklin

Page 134

air pass out at E, which striking forcibly against the water
abaft must push the boat forward. If there is added an air-vessel
F properly valved and placed, the force would continue to act while
a fresh stroke is taken with the lever. The boat-man might stand
with his back to the stern, and putting his hands behind him, work
the motion by taking hold of the cross bar at B, while another
should steer; or if he had two such pumps, one on each side of the
stern, with a lever for each hand, he might steer himself by working
occasionally more or harder with either hand, as watermen now do
with a pair of sculls. There is no position in which the body of a
man can exert more strength than in pulling right upwards. To obtain
more swiftness, greasing the bottom of a vessel is sometimes used,
and with good effect. I do not know that any writer has hitherto
attempted to explain this. At first sight one would imagine, that
though the friction of a hard body, sliding on another hard body,
and the resistance occasioned by that friction, might be diminished
by putting grease between them, yet that a body sliding on a fluid,
such as water, should have no need of, nor receive any advantage
from such greasing. But the fact is not disputed. And the reason
perhaps may be this--The particles of water have a mutual attraction,
called the attraction of adhesion. Water also adheres to wood, and
to many other substances, but not to grease: on the contrary they
have a mutual repulsion, so that it is a question whether when oil
is poured on water, they ever actually touch each other; for a drop
of oil upon water, instead of sticking to the spot where it falls,
as it would if it fell on a looking-glass, spreads instantly to an
immense distance in a film extremely thin, which it could not easily
do if it touched and rubbed or adhered even in a small degree to the
surface of the water. Now the adhesive force of water to itself, and
to other substances, may be estimated from the weight of it necessary
to separate a drop, which adheres, while growing, till it has weight
enough to force the separation and break the drop off. Let us suppose
the drop to be the size of a pea, then there will be as many of these
adhesions as there are drops of that size touching the bottom of a
vessel, and these must be broken by the

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

Page 2
e.
Page 3
From a bent wire (_a_) sticking in the table, let a small linen thread (_b_) hang down within half an inch of the electrised phial (_c_).
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
e.
Page 12
But if a man holds in his hands two bottles, one fully electrify'd, the other not at all, and brings their hooks together, he has but half a shock, and the bottles will both remain half electrified, the one being half discharged, and the other half charged.
Page 14
13.
Page 18
'Tis made of a thin round plate of window-glass, seventeen inches diameter, well gilt on both sides, all but two inches next the edge.
Page 23
26.
Page 25
Dip both sets in water, and some cohering to each ball they will represent air loaded.
Page 29
56.
Page 30
From these three things, the extreme subtilty of the electrical matter, the mutual repulsion of its parts, and the strong attraction between them and other matter, arise this effect, that when a quantity of electrical matter, is applied to a mass of common matter, of any bigness or length within our observation (which has not already got its quantity) it is immediately and equally diffused through the whole.
Page 32
15.
Page 37
I say, if these things are so, may not the knowledge of this power of points be of use to mankind, in preserving houses, churches, ships, &c.
Page 38
We have also melted gold, silver, and copper, in small quantities, by the electrical flash.
Page 39
Sometimes the stain spreads a little wider than the breadth of the leaf, and looks brighter at the edge, as by inspecting closely you may observe in these.
Page 41
And if you hold a plate under it at six or eight inches distance, and cease turning the Globe, when the electrical atmosphere of the conductor grows small, it will descend to the plate and swim back again several times with the same fish-like motion, greatly to the entertainment of spectators.
Page 45
As this charg'd part of the globe comes round to the cushion again, the outer surface delivers its overplus fire into the cushion, the opposite inner surface receiving at the same time an equal quantity from the.
Page 47
You may lessen its whole quantity by drawing out a part, which the whole body will again resume; but of glass you can only lessen the quantity contain'd in one of its surfaces; and not that, but by supplying an equal quantity at the same time to the other surface; so that the whole glass may always have the same quantity in the two surfaces, their two different quantities being added together.
Page 48
For though the effluvia of cinnamon, and the electrical fluid should mix within the globe, they would never come out together through the pores of the glass, and so go to the prime conductor; for the electrical fluid itself cannot come through; and the prime conductor is always supply'd from the cushion, and that from the floor.
Page 50
Thus the bottle is charged with its own fire, no other being to be had while the glass plate is under the cushion.