Front Page Titles (by Subject) LXXXVII: TO CADWALLADER COLDEN - The Works of Benjamin Franklin, Vol. II Letters and Misc. Writings 1735-1753
Return to Title Page for The Works of Benjamin Franklin, Vol. II Letters and Misc. Writings 1735-1753
The Online Library of Liberty
A project of Liberty Fund, Inc.
LXXXVII: TO CADWALLADER COLDEN - Benjamin Franklin, The Works of Benjamin Franklin, Vol. II Letters and Misc. Writings 1735-1753 
The Works of Benjamin Franklin, including the Private as well as the Official and Scientific Correspondence, together with the Unmutilated and Correct Version of the Autobiography, compiled and edited by John Bigelow (New York: G.P. Putnam’s Sons, 1904). The Federal Edition in 12 volumes. Vol. II (Letters and Misc. Writings 1735-1753).
About Liberty Fund:
Liberty Fund, Inc. is a private, educational foundation established to encourage the study of the ideal of a society of free and responsible individuals.
The text is in the public domain.
Fair use statement:
This material is put online to further the educational goals of Liberty Fund, Inc. Unless otherwise stated in the Copyright Information section above, this material may be used freely for educational and academic purposes. It may not be used in any way for profit.
TO CADWALLADER COLDEN
read at the royal society, november 11, 1756
Philadelphia, 23 April, 1752.
In considering your favor of the 16th past, I recollected my having wrote you answers to some queries concerning the difference between electrics per se and non-electrics, and the effects of air in electrical experiments, which, I apprehend, you may not have received. The date I have forgotten.
We have been used to call those bodies electrics per se, which would not conduct the electric fluid. We once imagined that only such bodies contained that fluid; afterwards that they had none of it, and only educed it from other bodies; but further experiments showed our mistake. It is to be found in all matter we know of; and the distinction of electrics per se and non-electrics should now be dropped as improper, and that of conductors and non-conductors assumed in its place, as I mentioned in those answers.
I do not remember any experiment by which it appeared that high-rectified spirit will not conduct; perhaps you have made such. This I know, that wax, rosin, brimstone, and even glass, commonly reputed electrics per se, will, when in a fluid state, conduct pretty well. Glass will do it when only red-hot. So that my former position, that only metals and water were conductors, and other bodies more or less such as they partook of metal or moisture, was too general.
Your conception of the electric fluid, that it is incomparably more subtile than air, is undoubtedly just. It pervades dense matter with the greatest ease; but it does not seem to mix or incorporate willingly with mere air, as it does with other matter. It will not quit common matter to join with air. Air obstructs, in some degree, its motion. An electric atmosphere cannot be communicated at so great a distance, by far, through intervening air as through a vacuum. Who knows, then, but there may be, as the ancients thought, a region of this fire above our atmosphere, prevented by our air and its own too great distance for attraction, from joining our earth? Perhaps where the atmosphere is rarest this fluid may be densest, and nearer the earth, where the atmosphere grows denser, this fluid may be rarer, yet some of it be low enough to attach itself to our highest clouds, and thence they, becoming electrified may be attracted by and descend towards the earth and discharge their watery contents, together with that ethereal fire. Perhaps the auroræ boreales are currents of this fluid in its own region, above our atmosphere, becoming from their motion, visible. There is no end to conjectures. As yet we are but novices in this branch of natural knowledge.
You mention several differences of salts in electrical experiments. Were they all equally dry? Salt is apt to acquire moisture from a moist air, and some sorts more than others. When perfectly dried by lying before a fire, or on a stove, none that I have tried will conduct any better than so much glass.
New flannel, if dry and warm, will draw the electric fluid from non-electrics, as well as that which has been worn.
I wish you had the convenience of trying the experiments you seem to have such expectations from, upon various kinds of spirits, salts, earth, &c. Frequently, in a variety of experiments, though we miss what we expected to find, yet something valuable turns out, something surprising and instructing, though unthought of.
I thank you for communicating the illustration of the theorem concerning light. It is very curious. But I must own I am much in the dark about light. I am not satisfied with the doctrine that supposes particles of matter, called light, continually driven off from the sun’s surface, with a swiftness so prodigious! Must not the smallest particle conceivable have, with such a motion, a force exceeding that of a twenty-four pounder discharged from a cannon? Must not the sun diminish exceedingly by such a waste of matter; and the planets, instead of drawing nearer to him, as some have feared, recede to greater distances through the lessened attraction? Yet these particles, with this amazing motion, will not drive before them, or remove the least and lightest dust they meet with. And the sun, for aught we know, continues of his ancient dimensions, and his attendants move in their ancient orbits.
May not all the phenomena of light be more conveniently solved, by supposing universal space filled with a subtile elastic fluid, which, when at rest, is not visible, but whose vibrations affect that fine sense in the eye, as those of air do the grosser organs of the ear? We do not, in the case of sound, imagine that any sonorous particles are thrown off from a bell, for instance, and fly in straight lines to the ear; why must we believe that luminous particles leave the sun and proceed to the eye? Some diamonds, if rubbed, shine in the dark, without losing any part of their matter. I can make an electrical spark as big as the flame of a candle, much brighter, and therefore, visible farther; yet this is without fuel; and I am persuaded no part of the electric fluid flies off in such case to distant places, but all goes directly, and is to be found in the place to which I destine it. May not different degrees of the vibration of the above-mentioned universal medium occasion the appearances of different colors? I think the electric fluid is always the same; yet I find that weaker and stronger sparks differ in apparent color; some white, blue, purple, red; the strongest, white; weak ones, red. Thus different degrees of vibration given to the air produce the seven different sounds in music, analogous to the seven colors, yet the medium, air, is the same.
If the sun is not wasted by expense of light, I can easily conceive that he shall otherwise always retain the same quantity of matter; though we should suppose him made of sulphur constantly flaming. The action of fire only separates the particles of matter; it does not annihilate them. Water, by heat raised in vapor, returns to the earth in rain; and if we could collect all the particles of burning matter that go off in smoke, perhaps they might, with the ashes, weigh as much as the body before it was fired; and if we could put them into the same position with regard to each other, the mass would be the same as before, and might be burnt over again. The chemists have analyzed sulphur, and find it composed, in certain proportions, of oil, salt, and earth; and having by the analysis discovered those proportions, they can, of those ingredients, make sulphur. So we have only to suppose, that the parts of the sun’s sulphur, separated by fire, rise into his atmosphere, and there, being freed from the immediate action of the fire, they collect into cloudy masses, and growing by degrees too heavy to be longer supported, they descend to the sun and are burnt over again. Hence the spots appearing on his face, which are observed to diminish daily in size, their consuming edges being of particular brightness.
It is well we are not, as poor Galileo was, subject to the Inquisition for philosophical heresy. My whispers against the orthodox doctrine, in private letters, would be dangerous; but your writing and printing would be highly criminal. As it is, you must expect some censure; but one heretic will surely excuse another.
I am heartily glad to hear more instances of the success of the poke-weed in the cure of that horrible evil to the human body, a cancer. You will deserve highly of mankind for the communication. But I find in Boston they are at a loss to know the right plant, some asserting it is what they call mechoachan, others other things. In one of their late papers it is publicly requested that a perfect description may be given of the plant, its places of growth, &c. I have mislaid the paper, or would send it to you. I thought you had described it pretty fully. I am, Sir, &c.,