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

By Benjamin Franklin

Page 60

Dr. Franklin, stating, that since he had first made
the observation concerning the south or south west winds succeeding
an aurora, he had found it invariably obtaining in twenty-three
instances; and he adds in a note a fresh confirming instance. In
reply, Dr. Franklin makes the following conjecture.]


The _Auroræ Boreales_, though visible almost every night of clear
weather in the more northern regions and very high in the atmosphere,
can scarce be visible in England, but when the atmosphere is pretty
clear of clouds for the whole space between us and those regions;
and therefore are seldom visible here. This extensive clearness may
have been produced by a long continuance of northerly winds. When
the winds have long continued in one quarter, the return is often
violent. Allowing the fact so repeatedly observed by Mr. Winn,
perhaps this may account for the violence of the southerly winds,
that soon follow the appearance of the aurora on our coasts.

FOOTNOTES:

[12] If I mistake not, this paper was read to the Royal Academy of
Sciences, at Paris, at the meeting held immediately after Easter,
1779. B. V[13].

[13] For an explanation of the signature B. V. see the note in page
399 of Vol. I. _Editor._




TO DR. L.[14] AT CHARLES-TOWN, SOUTH-CAROLINA.

_On Cold produced by Evaporation._


_New-York, April_ 14, 1757.

SIR,

It is a long time since I had the pleasure of a line from you; and,
indeed, the troubles of our country, with the hurry of business
I have been engaged in on that account, have made me so bad a
correspondent, that I ought not to expect punctuality in others.

But being about to embark for England, I could not quit the continent
without paying my respects to you, and, at the same time, taking
leave to introduce to your acquaintance a gentleman of learning and
merit, colonel Henry Bouquet, who does me the favour to present you
this letter, and with whom I am sure you will be much pleased.

Professor Simpson, of Glasgow, lately communicated to me some
curious experiments of a physician of his acquaintance, by which it
appeared, that an extraordinary degree of cold, even to freezing,
might be produced by evaporation. I have not had leisure to repeat
and examine more than the first and easiest of them, _viz._--Wet the
ball of a thermometer by a feather dipt in spirit of wine, which
has been kept in the same room, and has, of course, the same degree
of heat or cold. The mercury sinks presently three or four degrees,
and the quicker, if, during the evaporation, you blow

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

Page 3
The shock to the nerves (or convulsion rather) is occasion'd by the sudden passing of the fire through the body in its way from the top to the bottom of the bottle.
Page 4
As soon as you draw any fire out from the upper part by touching the wire, the lower part of the bottle draws an equal quantity in by the thread.
Page 7
less, according to the quantity of Electricity.
Page 10
Touch the wire with your finger, and then touch his hand or face; there are sparks every time.
Page 12
8, 9, 10, 11.
Page 14
Then to find if it resided in the water, being crouded into and condensed in it, as connfi'd by the glass, which had been our former opinion, we electrify'd the bottle again, and placing it on glass, drew out the wire and cork as before; then taking up the bottle we decanted all its water into an empty bottle, which likewise stood on glass; and taking up that other bottle, we expected if the force resided in the water, to find a shock from it; but there was none.
Page 16
If the cut is through the picture 'tis not the worse.
Page 18
When it is well charg'd it begins to move; the bullet nearest to a pillar moves towards the thimble on that pillar, and passing by electrifies it and then pushes itself from it; the succeeding bullet, which communicates with the other surface of the glass, more strongly attracts that thimble on account of its being before electrified by the other bullet; and thus the wheel encreases its motion till it comes to such a height as that the resistance of the air regulates it.
Page 20
28.
Page 23
For when vapours rise into the coldest region above the earth, the cold will not diminish the electrical fire, if it doth the common.
Page 24
If much loaded, the electrical fire is at once taken from the whole cloud; and, in leaving it, flashes brightly and cracks loudly; the particles instantly coalescing for want of that fire, and falling in a heavy shower.
Page 33
The extremities of the portions of atmosphere over these angular parts are likewise at a greater distance from the electrified body, as may be seen by the inspection of the above figure; the point of the atmosphere of the angle C, being much farther from C, than any other part of the atmosphere over the lines C, B, or B, A: And besides the distance arising from the nature of the figure, where the attraction is less, the particles will naturally expand to a greater distance by their mutual repulsion.
Page 34
But the force with which the electrified body retains its atmosphere by attracting it, is proportioned to the surface over which the particles are placed; i.
Page 36
Nay, even if the needle be placed upon the floor near the punch, its point upwards, the end of the punch, tho' so much higher than the needle, will not attract the scale and receive its fire, for the needle will get it and convey it away, before it comes nigh enough for the punch to act.
Page 37
from the stroke of lightning, by directing us to fix on the highest parts of those edifices, upright rods of iron made sharp as a needle, and gilt to prevent rusting, and from the foot of those rods a wire down the outside of the building into the ground, or down round one of the shrouds of a ship, and down her side till it reaches the water? Would not these pointed rods probably draw the electrical fire silently out of a cloud before it came nigh enough to strike, and thereby secure us from that most sudden and terrible mischief? 21.
Page 38
The manner is this: Take leaf gold, leaf silver, or leaf gilt copper, commonly called leaf brass or _Dutch_ gold: cut off from the leaf long narrow strips the breadth of a straw.
Page 43
And by this, that we cannot from a mass of glass draw a quantity of electrical fire, or electrify the whole mass _minus_, as we can a mass of metal.
Page 44
When the glass has received and, by its attraction, forced closer together so much of this electrified fluid, as that the power of attracting and condensing in the one, is equal to the power of expansion in the other, it can imbibe no more, and that remains its constant whole quantity; but each surface would receive more, if the repellency of what is in the opposite surface did not resist its entrance.
Page 48
And besides, when the globe is filled with cinnamon, or other non-electric, no electrical fluid can be obtain'd from its outer surface, for the reason before-mentioned.
Page 53
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