if the tight room is kept shut; for were there any force capable of
drawing constantly so much air out of it, it must soon be exhausted
like the receiver of an air-pump, and no animal could live in it.
Those therefore who stop every crevice in a room to prevent the
admission of fresh air, and yet would have their chimney carry up
the smoke, require inconsistencies, and expect impossibilities.
Yet under this situation, I have seen the owner of a new house, in
despair, and ready to sell it for much less than it cost, conceiving
it uninhabitable, because not a chimney in any one of its rooms would
carry off the smoke, unless a door or window were left open. Much
expence has also been made, to alter and amend new chimneys which
had really no fault; in one house particularly that I knew, of a
nobleman in Westminster, that expence amounted to no less than three
hundred pounds, _after_ his house had been, as he thought, finished
and all charges paid. And after all, several of the alterations were
ineffectual, for want of understanding the true principles.
_Remedies._ When you find on trial, that opening the door or a
window, enables the chimney to carry up all the smoke, you may be
sure that want of air _from without_, was the cause of its smoking.
I say _from without_, to guard you against a common mistake of those
who may tell you, the room is large, contains abundance of air,
sufficient to supply any chimney, and therefore it cannot be that the
chimney wants air. These reasoners are ignorant, that the largeness
of a room, if tight, is in this case of small importance, since it
cannot part with a chimney full of its air without occasioning so
much vacuum; which it requires a great force to effect, and could not
be borne if effected.
It appearing plainly, then, that some of the outward air must be
admitted, the question will be, how much is _absolutely necessary_;
for you would avoid admitting more, as being contrary to one of your
intentions in having a fire, viz. that of warming your room. To
discover this quantity, shut the door gradually while a middling
fire is burning, till you find that, before it is quite shut, the
smoke begins to come out into the room, then open it a little till
you perceive the smoke comes out no longer. There hold the door, and
observe the width of the open crevice between the edge of the door
and the rabbit it should shut into.
Yet, in buying goods, it is best to pay ready money, because he that sells upon credit expects to lose five per cent.Page 60
in all the learning of the white people.Page 62
You saw that we, who understand and practise those rules, believed all your stories; why do you refuse to believe ours?" When any of them come into our towns, our people are apt to crowd around them, gaze upon them, and incommode them where they desire to be private; this they esteem great rudeness, and the effect of the want of instruction in the rules of civility and good manners.Page 69
He argued on the injustice of applying by innuendoes, general assertions concerning principles of government, as overt acts to prove the writer was compassing the death of the king; for then no man could write of things done even by our ancestors, in defence of the constitution and freedom of England, without exposing himself to capital danger.Page 75
Tremble, thou wretch, That hast within thee undivulged crimes Unwhipp'd of justice! "Close pent-up guilt, Raise your concealing continents, and ask These.Page 85
Franklin, as one of the American plenipotentiaries, was principally concerned, viz.Page 98
"New-York, May 30, 1757 "DEAR SISTER, "I have before me yours of the 9th and 16th instant.Page 106
The present ministry are perplexed, and the measures they will finally take on the occasion are yet unknown.Page 118
During the same time sixty thousand children have been born in America.Page 124
You tell me that she will certainly cheat us, and that she despises us already.Page 180
Mitchell's paper on the strata of the earth with thanks.Page 181
_--Read in the American Philosophical Society January 15, 1790.Page 182
Has the question, how came the earth by its magnetism, ever been considered? Is it likely that _iron ore_ immediately existed when this globe was at first formed; or may it not rather be supposed a gradual production of time? If the earth is at present magnetical, in virtue of the masses of iron ore contained in it, might not some ages pass before it had magnetic polarity? Since iron ore may exist without that polarity, and, by being placed in certain circumstances, may obtain it from an external cause, is it not possible that the earth received its magnetism from some such cause? In short, may not a magnetic power exist throughout our system, perhaps through all systems, so that if men could make a voyage in the starry regions, a compass might be of use? And may not such universal magnetism, with its uniform direction, be serviceable in keeping the diurnal revolution of a planet more steady to the same axis? Lastly, as the poles of magnets may be changed by the presence of stronger magnets, might not, in ancient times, the near passing of some large comet, of greater magnetic power than this globe of ours, have been a means of changing its poles, and thereby wrecking and deranging its surface, placing in different regions the effect of centrifugal force, so as to raise the waters of the sea in some, while they were depressed in others? Let me add another question or two, not relating indeed to magnetism, but, however, to the theory of the earth.Page 191
The inhabitants, Dr.Page 197
a conductor, the fluid quits them and strikes into the earth.Page 199
Paris, September, 1767.Page 208
A fluid, moving from all points horizontally towards a centre, must, at that centre, either ascend or descend.Page 216
I intended to observe it, but was prevented by a northeast storm, which came on about seven, with thick clouds as usual, that quite obscured the whole hemisphere.Page 220
Thus, if you take, as I have done, a square bar of lead, four inches long and one inch thick, together with three pieces of wood planed to the same dimensions, and lay them on a smooth board, fixed so as not to be easily separated or moved, and pour into the cavity they form as much melted lead as will fill it, you will see the melted lead chill and become firm on the side next the leaden bar some time before it chills on the other three sides in contact with the wooden bars, though, before the lead was poured in, they might all be supposed to have the same degree of heat or coldness, as they had been exposed in the same room to the same air.Page 238
I will, however, take this opportunity of repeating those particulars to you which I mentioned in our last conversation, as, by perusing them at your leisure, you may possibly imprint them so in your memory as, on occasion, to be of some use to you.