Craven-street, Saturday evening, past 10.
The question you ask me is a very sensible one, and I shall be glad if I can give you a satisfactory answer. There are two ways of contracting a chimney; one by contracting the opening before the fire, the other by contracting the funnel above the fire. If the funnel above the fire is left open in its full dimensions, and the opening before the fire is contracted, then the coals, I imagine, will burn faster, because more air is directed through the fire, and in a stronger stream; that air which before passed over it and on each side of it, now passing through it. This is seen in narrow stove chimneys, when a sacheverell or blower is used, which still more contracts the narrow opening. But if the funnel only above the fire is contracted, then, as a less stream of air is passing up the chimney, less must pass through the fire, and, consequently, it should seem that the consuming of the coals would rather be checked than augmented by such contraction. And this will also be the case when both the opening before the fire and the funnel above the fire are contracted, provided the funnel above the fire is more contracted in proportion than the opening before the fire. So, you see, I think you had the best of the argument; and as you, notwithstanding, gave it up in complaisance to the company, I think you had also the best of the dispute. There are few, though convinced, that know how to give up even an error they have been once engaged in maintaining; there is, therefore, the more merit in dropping a contest where one thinks one's self right; it is at least respectful to those we converse with. And, indeed, all our knowledge is so imperfect, and we are, from a thousand causes, so perpetually subject to mistake and error, that positiveness can scarce ever become even the most knowing; and modesty in advancing any opinion, however plain and true we may suppose it, is always decent, and generally more likely to procure assent. Pope's rule,
To speak, though sure, with seeming diffidence,
is therefore a good one; and if I had ever seen in your conversation the least deviation from it, I should earnestly recommend it to your observation. I am, &c.,
B. Franklin.
OBSERVATIONS ON THE PREVAILING DOCTRINES OF LIFE AND DEATH.
* * Your observations on the causes of death, and the experiments which you propose for recalling to life those who appear to be killed by lightning, demonstrate equally your sagacity and your humanity. It appears that the doctrines of life and death, in general, are yet but little understood.
A toad buried in sand will live, it is said, till the sand becomes petrified: and then, being enclosed in the stone, it may still live for we know not how many ages. The facts which are cited in support of this opinion are too numerous and too circumstantial not to deserve a certain degree of credit. As we are accustomed to see all the animals with which we are acquainted eat and drink, it appears to us difficult to conceive how a toad can be supported in such a dungeon: but if we reflect that the necessity of nourishment, which animals experience in their ordinary state, proceeds from the continual waste of their substance by perspiration, it will appear less incredible that some animals, in a torpid state, perspiring less because they use no exercise, should have less need of aliment; and that others, which are covered with scales or shells which stop perspiration, such as land and sea turtles, serpents, and some species of fish, should be able to subsist a considerable time without any nourishment whatever. A plant, with its flowers, fades and dies immediately if exposed to the air without having its root immersed in a humid soil, from which it may draw a sufficient quantity of moisture to supply that which exhales from its substance and is carried off continually by the air. Perhaps, however, if it were buried in quicksilver, it might preserve, for a considerable space of time, its vegetable life, its smell, and colour. If this be the case, it might prove a commodious method of transporting from distant countries those delicate plants which are unable to sustain the inclemency of the weather at sea, and which require particular care and attention. I have seen an instance of common flies preserved in a manner somewhat similar. They had been drowned in Madeira wine, apparently about the time when it was bottled in Virginia to be sent hither (to London). At the opening of one of the bottles, at the house of a friend where I then was, three drowned flies fell into the first glass that was filled. Having heard it remarked that drowned flies were capable of being revived by the rays of the sun, I proposed making the experiment upon these: they were therefore exposed to the sun upon a sieve, which had been employed to strain them out of the wine. In less than three hours, two of them began by degrees to recover life. They commenced by some convulsive motions of the thighs, and at length they raised themselves upon their legs, wiped their eyes with their fore-feet, beat and brushed their wings with their hind-feet, and soon after began to fly, finding themselves in Old England, without knowing how they came thither. The third continued lifeless till sunset, when, losing all hopes of him, he was thrown away.