Memoirs of Benjamin Franklin; Written by Himself. [Vol. 2 of 2]

3. The air may be the cause of earthquakes; for the air being a collection of fumes and vapours raised from the earth and water, if it be pent up in too narrow viscera of the earth, the subterraneous or its own native heat rarefying and expanding it, the force wherewith it endeavours to escape may shake the earth; hence there arises divers species of earthquakes, according to the different position, quantity, &c., of the imprisoned aura.

Lastly, fire is a principal cause of earthquakes; both as it produces the aforesaid subterraneous aura or vapours, and as this aura or spirit, from the different matter and composition whereof arise sulphur, bitumen, and other inflammable matters, takes fire, either from other fire it meets withal, or from its collision against hard bodies, or its intermixture with other fluids; by which means, bursting out into a greater compass, the place becomes too narrow for it, so that, pressing against it on all sides, the adjoining parts are shaken, till, having made itself a passage, it spends itself in a volcano or burning mountain.

But to come nearer to the point. Dr. Lister is of opinion that the material cause of thunder, lightning, and earthquakes, is one and the same, viz., the inflammable breath of the pyrites, which is a substantial sulphur, and takes fire of itself.

The difference between these three terrible phenomena he takes only to consist in this: that the sulphur in the former is fired in the air, and in the latter under ground. Which is a notion Pliny had long before him: "Quid enim," says he, "aliud est in terrâ tremor, quam in nube tonitru?" For wherein does the trembling of the earth differ from that occasioned by thunder in the clouds?

This he thinks abundantly indicated by the same sulphurous smell being found in anything burned with lightning, and in the waters, &c., cast up in earthquakes, and even in the air before and after them.

Add that they agree in the manner of the noise which is carried on, as in a train fired; the one, rolling and rattling through the air, takes fire as the vapours chance to drive; as the other, fired under ground in like manner, moves with a desultory noise.

Thunder, which is the effect of the trembling of the air, caused by the same vapours dispersed through it, has force enough to shake our houses; and why there may not be thunder and lightning under ground, in some vast repositories there, I see no reason; especially if we reflect that the matter which composes the noisy vapour above us is in much larger quantities under ground.

That the earth abounds in cavities everybody allows; and that these subterraneous cavities are, at certain times and in certain seasons, full of inflammable vapours, the damps in mines sufficiently witness, which, fired, do everything as in an earthquake, save in a lesser degree.

Add that the pyrites alone, of all the known minerals, yields this inflammable vapour, is highly probable; for that no mineral or ore whatsoever is sulphurous, but as it is wholly or in part a pyrites, and that there is but one species of brimstone which the pyrites naturally and only yields. The sulphur vive, or natural brimstone, which is found in and about the burning mountains, is certainly the effects of sublimation, and those great quantities of it said to be found about the skirts of volcanoes is only an argument of the long duration and vehemence of those fires. Possibly the pyrites of the volcanoes, or burning mountains, may be more sulphurous than ours; and, indeed, it is plain that some of ours in England are very lean, and hold but little sulphur; others again very much, which may be some reason why England is so little troubled with earthquakes, and Italy, and almost all round the Mediterranean Sea, so much; though another reason is, the paucity of pyrites in England.

Comparing our earthquakes, thunder, and lightning, with theirs, it is observed that there it lightens almost daily, especially in summer-time, here seldom; there thunder and lightning is of long duration, here it is soon over; there the earthquakes are frequent, long, and terrible, with many paroxysms in a day, and that for many days; here very short, a few minutes, and scarce perceptible. To this purpose the subterraneous caverns in England are small and few compared to the vast vaults in those parts of the world; which is evident from the sudden disappearance of whole mountains and islands.

Dr. Woodward gives us another theory of earthquakes. He endeavours to show that the subterraneous heat or fire (which is continually elevating water out of the abyss, to furnish the earth with rain, dew, springs, and rivers), being stopped in any part of the earth, and so diverted from its ordinary course by some accidental glut or obstruction in the pores or passages through which it used to ascend to the surface, becomes, by such means, preternaturally assembled in a greater quantity than usual into one place, and therefore causeth a great rarefaction and intumescence of the water of the abyss, putting it into great commotions and disorders, and at the same time making the like effort on the earth, which, being expanded upon the face of the abyss, occasions that agitation and concussion we call an earthquake.

This effort in some earthquakes, he observes, is so vehement, that it splits and tears the earth, making cracks and chasms in it some miles in length, which open at the instant of the shock, and close again in the intervals between them; nay, it is sometimes so violent that it forces the superincumbent strata, breaks them all throughout, and thereby perfectly undermines and ruins the foundation of them; so that, these failing, the whole tract, as soon as the shock is over, sinks down into the abyss, and is swallowed up by it, the water thereof immediately rising up and forming a lake in the place where the said tract before was. That this effort being made in all directions indifferently, the fire, dilating and expanding on all hands, and endeavouring to get room and make its way through all obstacles, falls as foul on the waters of the abyss beneath as on the earth above, forcing it forth, which way soever it can find vent or passage, as well through its ordinary exits, wells, springs, and the outlets of rivers, as through the chasms then newly opened, through the camini or spiracles of Ætna, or other neighbouring volcanoes, and those hiatuses at the bottom of the sea whereby the abyss below opens into it and communicates with it. That as the water resident in the abyss is, in all parts of it, stored with a considerable quantity of heat, and more especially in those where those extraordinary aggregations of this fire happen, so likewise is the water which is thus forced out of it, insomuch that, when thrown forth and mixed with the waters of wells, or springs of rivers and the sea, it renders them very sensibly hot.

He adds, that though the abyss be liable to those commotions in all parts, yet the effects are nowhere very remarkable except in those countries which are mountainous, and, consequently, stony or cavernous underneath; and especially where the disposition of the strata is such that those caverns open the abyss, and so freely admit and entertain the fire which, assembling therein, is the cause of the shock; it naturally steering its course that way where it finds the readiest reception, which is towards those caverns. Besides, that those parts of the earth which abound with strata of stone or marble, making the strongest opposition to this effort, are the most furiously shattered, and suffer much more by it than those which consist of gravel, sand, and the like laxer matter, which more easily give way, and make not so great resistance. But, above all, those countries which yield great store of sulphur and nitre are by far the most injured by earthquakes; those minerals constituting in the earth a kind of natural gunpowder, which, taking fire upon this assemblage and approach of it, occasions that murmuring noise, that subterraneous thunder, which is heard rumbling in the bowels of the earth during earthquakes, and by the assistance of its explosive power renders the shock much greater, so as sometimes to make miserable havoc and destruction.

And it is for this reason that Italy, Sicily, Anatolia, and some parts of Greece, have been so long and often alarmed and harassed by earthquakes; these countries being all mountainous and cavernous, abounding with stone and marble, and affording sulphur and nitre in great plenty.

Farther, that Ætna, Vesuvius, Hecla, and the other volcanoes, are only so many spiracles, serving for the discharge of this subterraneous fire, when it is thus preternaturally assembled. That where there happens to be such a structure and conformation of the interior part of the earth, as that the fire may pass freely, and without impediment, from the caverns wherein it assembles unto those spiracles, it then readily gets out, from time to time, without shaking or disturbing the earth; but where such communication is wanting, or passage not sufficiently large and open, so that it cannot come at the spiracles, it heaves up and shocks the earth with greater or lesser impetuosity, according to the quantity of fire thus assembled, till it has made its way to the mouth of the volcano. That, therefore, there are scarce any countries much annoyed by earthquakes but have one of these fiery vents, which are constantly in flames when any earthquake happens, as disgorging that fire which, while underneath, was the cause of the disaster. Lastly, that were it not for these diverticula, it would rage in the bowels of the earth much more furiously, and make greater havoc than it doth.

We have seen what fire and water may do, and that either of them are sufficient for all the phenomena of earthquakes; if they should both fail, we have a third agent scarce inferior to either of them; the reader must not be surprised when we tell him it is air.

Monsieur Amontons, in his Mémoires de l'Académie des Sciences, An. 1703, has an express discourse to prove, that on the foot of the new experiments of the weight and spring of the air, a moderate degree of heat may bring the air into a condition capable of causing earthquakes. It is shown that at the depth of 43,528 fathoms below the surface of the earth, air is only one fourth less heavy than mercury. Now this depth of 43,528 fathoms is only a seventy-fourth part of the semi-diameter of the earth. And the vast sphere beyond this depth, in diameter 6,451,538 fathoms, may probably be only filled with air, which will be here greatly condensed, and much heavier than the heaviest bodies we know in nature. But it is found by experiment that, the more air is compressed, the more does the same degree of heat increase its spring, and the more capable does it render it of a violent effect; and that, for instance, the degree of heat of boiling water increases the spring of the air above what it has in its natural state, in our climate, by a quantity equal to a third of the weight wherewith it is pressed. Whence we may conclude that a degree of heat, which on the surface of the earth will only have a moderate effect, may be capable of a very violent one below. And as we are assured that there are in nature degrees of heat much more considerable than boiling water, it is very possible there may be some whose violence, farther assisted by the exceeding weight of the air, may be more than sufficient to break and overturn this solid orb of 43,528 fathoms, whose weight, compared to that of the included air, would be but a trifle.

Chymistry furnishes us a method of making artificial earthquakes which shall have all the great effects of natural ones; which, as it may illustrate the process of nature in the production of these terrible phenomena under ground, we shall here add.

To twenty pounds of iron filings add as many of sulphur; mix, work, and temper the whole together with a little water, so as to form a mass half wet and half dry. This being buried three or four feet under ground, in six or seven hours time will have a prodigious effect; the earth will begin to tremble, crack, and smoke, and fire and flame burst through.

Such is the effect even of the two cold bodies in cold ground; there only wants a sufficient quantity of this mixture to produce a true Ætna. If it were supposed to burst out under the sea, it would produce a spout; and if it were in the clouds, the effect would be thunder and lightning.

An earthquake is defined to be a vehement shake or agitation of some considerable place, or part of the earth, from natural causes, attended with a huge noise like thunder, and frequently with an eruption of water, or fire, or smoke, or winds, &c.

They are the greatest and most formidable phenomena of nature. Aristotle and Pliny distinguish two kinds, with respect to the manner of the shake, viz., a tremour and a pulsation; the first being horizontal, in alternate vibrations, compared to the shaking of a person in an ague; the second perpendicular, up and down, their motion resembling that of boiling.

Agricola increases the number, and makes four kinds, which Albertus Magnus again reduces to three, viz., inclination, when the earth vibrates alternately from right to left, by which mountains have been sometimes brought to meet and clash against each other; pulsation, when it beats up and down, like an artery; and trembling, when it shakes and totters every way, like a flame.

The Philosophical Transactions furnish us with abundance of histories of earthquakes, particularly one at Oxford in 1665, by Dr. Wallis and Mr. Boyle. Another at the same place in 1683, by Mr. Pigot. Another in Sicily, in 1692-3, by Mr. Hartop, Father Alessandro Burgos, and Vin. Bonajutus, which last is one of the most terrible ones in all history.

It shook the whole island; and not only that, but Naples and Malta shared in the shock. It was of the second kind mentioned by Aristotle and Pliny, viz., a perpendicular pulsation or succussion. It was impossible, says the noble Bonajutus, for anybody in this country to keep on their legs on the dancing earth; nay, those that lay on the ground were tossed from side to side as on a rolling billow; high walls leaped from their foundations several paces.

The mischief it did is amazing; almost all the buildings in the countries were thrown down. Fifty-four cities and towns, besides an incredible number of villages, were either destroyed or greatly damaged. We shall only instance the fate of Catania, one of the most famous, ancient, and flourishing cities in the kingdom, the residence of several monarchs, and a university. "This once famous, now unhappy Catania," to use words of Father Burgos, "had the greatest share in the tragedy. Father Antonio Serovita, being on his way thither, and at the distance of a few miles, observed a black cloud, like night, hovering over the city, and there arose from the mouth of Mongibello great spires of flame, which spread all around. The sea, all of a sudden, began to roar and rise in billows, and there was a blow, as if all the artillery in the world had been at once discharged. The birds flew about astonished, the cattle in the fields ran crying, &c. His and his companion's horse stopped short, trembling; so that they were forced to alight. They were no sooner off but they were lifted from the ground above two palms. When, casting his eyes towards Catania, he with amazement saw nothing but a thick cloud of dust in the air. This was the scene of their calamity; for of the magnificent Catania there is not the least footstep to be seen." Bonajutus assures us, that of 18,914 inhabitants, 18,000 perished therein. The same author, from a computation of the inhabitants before and after the earthquake, in the several cities and towns, finds that near 60,000 perished out of 254,900.

Jamaica is remarkable for earthquakes. The inhabitants, Dr. Sloane informs us, expect one every year. The author gives the history of one in 1687; another horrible one, in 1692, is described by several anonymous authors. In two minutes' time it shook down and drowned nine tenths of the town of Port Royal. The houses sunk outright, thirty or forty fathoms deep. The earth, opening, swallowed up people, and they rose in other streets; some in the middle of the harbour, and yet were saved; though there were two thousand people lost, and one thousand acres of land sunk. All the houses were thrown down throughout the island. One Hopkins had his plantation removed half a mile from its place. Of all wells, from one fathom to six or seven, the water flew out at the top with a vehement motion. While the houses on the one side of the street were swallowed up, on the other they were thrown in heaps; and the sand in the street rose like waves in the sea, lifting up everybody that stood on it, and immediately dropping down into pits; and at the same instant, a flood of waters breaking in, rolled them over and over; some catching hold of beams and rafters, &c. Ships and sloops in the harbour were overset and lost; the Swan frigate particularly, by the motion of the sea and sinking of the wharf, was driven over the tops of many houses.

It was attended with a hollow rumbling noise like that of thunder. In less than a minute three quarters of the houses, and the ground they stood on, with the inhabitants, were all sunk quite under water, and the little part left behind was no better than a heap of rubbish. The shake was so violent that it threw people down on their knees or their faces, as they were running about for shelter. The ground heaved and swelled like a rolling sea, and several houses, still standing, were shuffled and moved some yards out of their places. A whole street is said to be twice as broad now as before; and in many places the earth would crack, and open, and shut, quick and fast, of which openings two or three hundred might be seen at a time; in some whereof the people were swallowed up, others the closing earth caught by the middle and pressed to death, in others the heads only appeared. The larger openings swallowed up houses; and out of some would issue whole rivers of waters, spouted up a great height into the air, and threatening a deluge to that part the earthquake spared. The whole was attended with stenches and offensive smells, the noise of falling mountains at a distance, &c., and the sky in a minute's time was turned dull and reddish, like a glowing oven. Yet, as great a sufferer as Port Royal was, more houses were left standing therein than on the whole island besides. Scarce a planting-house or sugar-work was left standing in all Jamaica. A great part of them were swallowed up, houses, people, trees, and all at one gape; in lieu of which afterward appeared great pools of water, which, when dried up, left nothing but sand, without any mark that ever tree or plant had been thereon.

Above twelve miles from the sea the earth gaped and spouted out, with a prodigious force, vast quantities of water into the air, yet the greatest violences were among the mountains and rocks; and it is a general opinion, that the nearer the mountains, the greater the shake, and that the cause thereof lay there. Most of the rivers were stopped up for twenty-four hours by the falling of the mountains, till, swelling up, they found themselves new tracts and channels, tearing up in their passage trees, &c. After the great shake, those people who escaped got on board ships in the harbour, where many continued above two months; the shakes all that time being so violent, and coming so thick, sometimes two or three in an hour, accompanied with frightful noises, like a ruffling wind, or a hollow, rumbling thunder, with brimstone blasts, that they durst not come ashore. The consequence of the earthquake was a general sickness, from the noisome vapours belched forth, which swept away above three thousand persons.

After the detail of these horrible convulsions, the reader will have but little curiosity left for the less considerable phenomena of the earthquake at Lima in 1687, described by Father Alvarez de Toledo, wherein above five thousand persons were destroyed; this being of the vibratory kind, so that the bells in the church rung of themselves; or that at Batavia in 1699, by Witsen; that in the north of England in 1703, by Mr. Thoresby; or, lastly, those in New-England in 1663 and 1670, by Dr. Mather.

To David Rittenhouse New and curious Theory of Light and Heat.– Read in the American Philosophical Society, November 20, 1788

Universal space, as far as we know of it, seems to be filled with a subtile fluid, whose motion or vibration is called light.

This fluid may possibly be the same with that which, being attracted by, and entering into other more solid matter, dilutes the substance by separating the constituent particles, and so rendering some solids fluid, and maintaining the fluidity of others; of which fluid, when our bodies are totally deprived, they are said to be frozen; when they have a proper quantity, they are in health, and fit to perform all their functions; it is then called natural heat; when too much, it is called fever; and when forced into the body in too great a quantity from without, it gives pain, by separating and destroying the flesh, and is then called burning, and the fluid so entering and acting is called fire.

While organized bodies, animal or vegetable, are augmenting in growth, or are supplying their continual waste, is not this done by attracting and consolidating this fluid called fire, so as to form of it a part of their substance? And is it not a separation of the parts of such substance, which, dissolving its solid state, sets that subtile fluid at liberty, when it again makes its appearance as fire?

For the power of man relative to matter seems limited to the separating or mixing the various kinds of it, or changing its form and appearance by different compositions of it; but does not extend to the making or creating new matter, or annihilating the old. Thus, if fire be an original element or kind of matter, its quantity is fixed and permanent in the universe. We cannot destroy any part of it, or make addition to it; we can only separate it from that which confines it, and so set it at liberty; as when we put wood in a situation to be burned, or transfer it from one solid to another, as when we make lime by burning stone, a part of the fire dislodged in the fuel being left in the stone. May not this fluid, when at liberty, be capable of penetrating and entering into all bodies, organized or not, quitting easily in totality those not organized, and quitting easily in part those which are; the part assumed and fixed remaining till the body is dissolved?

Is it not this fluid which keeps asunder the particles of air, permitting them to approach, or separating them more in proportion as its quantity is diminished or augmented?

Is it not the greater gravity of the particles of air which forces the particles of this fluid to mount with the matters to which it is attached, as smoke or vapour?

Does it not seem to have a greater affinity with water, since it will quit a solid to unite with that fluid, and go off with it in vapour, leaving the solid cold to the touch, and the degree measurable by the thermometer?

The vapour rises attached to this fluid, but at a certain height they separate, and the vapour descends in rain, retaining but little of it, in snow or hail less. What becomes of that fluid? Does it rise above our atmosphere, and mix with the universal mass of the same kind?

Or does a spherical stratum of it, denser, as less mixed with air, attracted by this globe, and repelled or pushed up only to a certain height from its surface by the greater weight of air, remain there surrounding the globe, and proceeding with it round the sun?

In such case, as there may be a continuity of communication of this fluid through the air quite down to the earth, is it not by the vibrations given to it by the sun that light appears to us? And may it not be that every one of the infinitely small vibrations, striking common matter with a certain force, enters its substance, is held there by attraction, and augmented by succeeding vibrations till the matter has received as much as their force can drive into it?

Is it not thus that the surface of this globe is continually heated by such repeated vibrations in the day, and cooled by the escape of the heat when those vibrations are discontinued in the night, or intercepted and reflected by clouds?

Is it not thus that fire is amassed, and makes the greatest part of the substance of combustible bodies?