YOU may justly expect, that the great EARTHQUAKE, which so lately ^a spread terror, and threatened desolation throughout New-England, should take me off from my stated course of lectures, to inquire into the probable causes of so formidable a phaenomenon. The subject is curious, and at present engages the attention of many persons; and the discussion of it may help to extend your views.

An Earthquake, you all know, is an agitation or shaking of some considerable part of the earth, and that by natural causes; in contradistinction to the shaking of a small part of it by artifi­cial methods. The degrees of this shaking are very various;—from the small jarrings, which are but just perceptible, to those violent [...]uccu [...]ions, which have altered the face of whole c [...]un­tri [...]s. [Page 6] These shakings are for the most part (I believe, always) praeceded or attended by an hollow rumbling noise, something like what is called heavy thunder; which is usually greater or less, according to the degree of the shake. Naturalists have distin­gui [...]hed earthquakes into two kinds; one, when the motion is horizontal, or from side to side; the other, when it is perpendi­cular, or right up and down. This distinction may, for what I know, be just; and yet perhaps earthquakes more commonly consist in a kind of undulatory motion, which may include both the others. For as a wave of water, when raised to it's greatest height, subsides, and in subsiding spreads itself horizontally; so in like manner, a wave of earth, if I may be allowed the ex­pression, must in it's descent partake both of an horizontal and perpendicular motion at the same time. And for the same rea­son, it must have had both these motions in it's ascent; but those particles, which had been carried forward in one direction in the ascent, will return in a contrary direction in the descent. This has been evidently found to be the case in the more violent earthquakes; and probably the reason why it has not been uni­versally found so, was, the difficulty of distinguishing these two motions from one another, when each of them has been but small. Though the ancient AEgyptians and Ch [...]ld [...]ans are said to have been able to foretell earthquakes, yet it is very certain, from all the accounts we have, that these agitations of the earth do no where observe any order or regular period in their returns; but at sometimes, recur more frequently; at others, after longer intermissions. If therefore they pretended to foretell them at all, they must have done it, not from any knowledge they had of their nature and causes; but only by the vain arts of judicial a [...]trology;—a kind of learning, it seems, which, f [...]tile as it is, was held in high repute among them. No countries, of which we have any knowledge, are exempt from these agitations; but some are more subject to them than others; and it is observable, that those which abound most with combustible minerals, as fo [...]ile coals, [...]ulphur, nitre, &c. are the most exposed to them. Many of these countries, too, have certa [...]n mountains called vul­canos, which are almost perpetually burning, and throwing out [Page 7] fire, and smoke, and ashes; their entrails probably consisting chiefly of such sort of minerals. It is observed, however, that about the time of an earthquake in those places, these vulcano [...] rage more furiously, projecting stones and cinders to a great height in the air; and pouring out whole rivers of liquid fire, which carry such a devastation, wherever they run, as no human art can either prevent or repair. Several such there are in the M [...]lucca islands in the East-Indies, almost under the [...]quinocti­al; and Iceland, under the polar circle, has four or five, besides the noted Hecla. Vesuvio near Naples is very remarkable; but there is none more famous than that in Sicily, now known there by the name of Monte Gibello, as it was formerly by that of AEtna; whose eruptions VIRGIL has described in so picturesque a manner, that I cannot forbear repeating a few lines from him.

AEneid. III. 571. [...]eqq.

This description ^b of these phaenomena is perhaps not exceeded by any extant; except by those passages in the holy scriptures which ascribe these effects, as true philosophy does all those [Page 8] which we call natural effects, to the agency of GOD. It is [...] ‘who removeth the mountains, and they know not; who [...] them in his anger; who shaketh the earth out of [...], and the pillars thereof tremble.’ ‘HE looketh on [...], and it trembleth; HE toucheth the hills, and they [...]’ ‘The pillars of heaven tremble, and are astonished at [...] proof.’ Nothing can equal the sublimity, the gran­deur o [...] these images. But to proceed.

That the earth has been, in all ages, and in most parts of it, subject to these agitations, history affords us but too many proofs. It is not, however, my design to enter into a detail of the dismal events of this sort, left upon record. I shall only extract from authentic accounts a few of the most striking particulars, in order to give you some idea of the dire effects, which such convulsions of the earth are capable of producing.

Imagine then the earth trembling with a huge thundering noise, or heaving and swelling like a rolling sea:—now gaping in chasms of various sizes, and then immediately closing again; either swallowing up the unhappy persons who chanced to be over them, or crushing them to death by the middle:—from some, spouting up prodigious quantities of water to a vast height, or belching out hot, offensive and suffocating exhalations; while others are streaming with torrents of melted minerals:—some houses moving out of their places; others cracking and t [...]mbling into heaps of rubbish; and others again, not barely by whole streets, but by whole cities at a time, sinking down­right to a great depth in the earth, or under water:—on the shore, the sea roaring and rising in billows; or else retiring to a great distance from the land, and then violently returning like a flood to overwhelm it; vessels driven from their anchors; some overset and lost, others thrown up on the land:— [...]n one place, vast rocks slung down from mountains, and ch [...]ki [...]g up rivers, which, being then forced to find themselves new [...], sweep away such trees, houses, &c. as had escaped the fury of the shock; in another, mountains themselves sinking in a moment, and their places [...] by pools of water:—some people run­ning about pale, with fear, trembling for the event, and ignorant [Page 9] whither to fly for shelter; others thrown with violence down on the ground, not being able to keep on their feet; and others shrieking or groaning in the agonies of death:—even the brute creation manifesting all the signs of consternation and astonish­ment:—Imagine these things to yourselves, and you will then have a view, though but an imperfect one, of some of those images of horror and desolation, which accompany the more vi­olent earthquakes.

But I will dwell no longer on these tragical scenes. Those of you, who are desirous of farther information, may meet with it in the Philosophical Transactions; ^c particularly in the accounts of those horrible earthquakes, which almost desolated the islands of Ja­maica and Sicily. 63 years ago; in the latter of which it was computed, that about 60,000 persons perished; which was very near one quarter of the whole number of inhabitants. To re­lieve you and my self under such melancholy prospects, I will turn my thoughts to the theory of these most formidable phaeno­mena, as soon as I have made two or three observations on the earthquakes we lately felt.

GOD be thanked, all earthquakes are not formidable in so high a degree. Those of New-England, in particular, which have indeed greatly and justly alarm'd the inhabitants, have never destroyed them. For tho' this country, we know, has been visited with earthquakes from it's first settlement by the English; yet, so far as my information reaches, not a single life has been lost by any of them; and perhaps never so much damage done to our buildings as by the last great shock: As to which I would observe.

First, That it certainly began with an undulation of the earth, as I have been assured by some who were then awake; tho' I think it would not have been easily concluded from the effects, that the earth had had any other than an horizontal motion; those effects which were generally taken notice of, being chiefly, if not only, such, as a perpendicular motion would not, but an horizontal one would, have produced. Such, for instance, were the dashing of liquors over the sides of open vessels; the over­setting [Page 10] setting many things in houses; and the throwing of bricks from off the tops of chimnies to some distance. In order to estimate the velocity with which some were thrown from my chimney, I measured the greatest distance on the ground to which any of them had reach'd, and found it to be 30 feet; and the height of the chimney from which they fell was 32 feet. Now bodies fall thro' 16 feet nearly in one second of time; and the times, in which they fall thro' other heights, are in the subdupli­cate ratio of those heights. From whence it follows, that the velocity, wherewith those bricks were thrown off, was that of above 21 feet in 1" of time. For the subduplicate ratio of 32 to 16 is the same as the simple ratio of 30 to a little more than 21. It will be impossible, I believe, ever to determine with exactness the rea [...] spaces thro' which any of our buildings vibrated, in this reciprocating motion of the earth. It may be observ'd, however, that the shorter these vibrations are supposed to have been, the quicker or more frequent they must have been; the number of them in a given time being reciprocally as the length of each. Thus, for example, if each vibration had been of one foot in length, then th [...]re were 21 of them in 1" of time; but if each were of 6 [...] then there were 42 of them in a second; and so on. Possibly, some of these reciprocations might be as quick as those of a musical chord.

But it is not to be doubted, that the velocity, wherewith our buildings were agitated, was different in different places. It was different also, as I apprehend, at different heights. This I collect from the observation, that a key, which was thrown off a shelf in my house, was not thrown so far, in proportion to the height thro' which it fell, as the bri [...]ks were from the top of the chimney. Hence it appears, that our buildings were r [...]cked with a kind of angular motion, like that of a cradle; the upper parts of them moving swifter, or thro' greater spaces in the same time, than the lower. ^d This perf [...]ctly agrees with the idea of an [Page 11] undulatory motion of the earth; as you may clearly conceive by turning your thoughts to the case of a vessel floating at rest upon stagnant water, and then suddenly agitated by a great wave rolling under it. In the motion of ascent, the mast of the vessel would be thrown forward, in the same direction as the wave was moving; and in the motion of descent, backward, or in the con­trary direction; and in both these cases, the top of the must would move thro' greater spaces than the bottom.

[Page 12]As it is certain, that in the great shock, the earth had an hori­zontal motion; so it appears with the most sensible evidence to me, that in the shock we felt the Saturday evening following, at 27' after 8, there was a perpendicular motion of the earth. I was then sitting on a brick hearth, and felt the motion of the bricks distinctly under my feet. It was not a motion of the whole hearth together, either from side to side, or up and down; but of each brick separately by itself. Now as the bricks were contiguous, the only motion, which could be communicated to them separately, was in a perpendicular direction; and the sen­sation excited in me was exactly the same, as if some small so­lid body, by moving along under the hearth, had raised up the bricks successively, which immediately settled down again. The motion of the earth in this instance plainly appeared undu­latory to me; and this shock, I apprehend, was occasioned by one small wave of earth rolling along, but not with a very swift motion. For the velocity of it's progress was considerably less than that of sound, which moves about 13 miles in a mi­nute; as appeared from hence, that the roar of this earthquake might be heard at least half a minute before the shake was felt. Which also argues, that the shock began at some considerable distance from this place. The same remarks may be applied to the great shock; only this began with two at least, if not three waves, of much greater breadth and height. The latter part of this shock was tremulous, consisting chiefly in vibrations which succeeded one another with extreme quickness; and, as I take it, was owing to the efforts of the earth to recover the position, out of which it had been violently thrust, during the undulatory mo­tion: Much in the same manner, as the re [...]iprocations of a mu­sical chord are occasioned by it's endeavour [...] to restore it self to that situation, which it had before it was struck. As soon as the stroke, which bent it, ceases, the chord does not barely regain it's rectilinear figure, but bends itself almost as far the contrary way; and thus continues bending and unbending itself with great quickness, till it's motion is gradually destroyed, and at length it settles into a state of rest. Both these [...] ▪ then, seem [Page 13] evidently to have been of the undulatory kind; and to have dif­fered in degree only. ^e I would observe

Secondly, that the duration of the great shock was longer than has been usually observed. If my memory fails me not, even those earthquakes, which have brought on the most amazing ca­tastrophes, have commonly done their execution in one or two minutes; whereas this shock with us lasted at least four; tak­ing in the whole of the time, from the first agitation of the earth, till it was become perfectly quiet; though the violence of the shock did not last above half so long. This I am assured of, partly from the observations of some Gentlemen, who were up, and looked on their watches, when it began and ended; and partly from my own, which were as follows. The preceding noon, I had adjusted both my clock and watch, by a meridian line; and the following noon I found that the watch had kept time exactly. Being awaked by the earthquake, I lay till the violence of it seemed to be over, for the second time; for it had a little abated before, as if it were going off, and then instantly began again with redoubled fury. Till then I forb [...]re to rise, because the agitation was so vehement, that I concluded it would be very difficult, if not impracticable, to go from the bed to the chimney, without being thrown down; and therefore thought it best not to attempt it. The space of time, in which I say awake, I cannot think to be much, if any thing, less than 2'. This was the conjecture I formed at that time; though it being but conjecture, I would not lay very great stress upon it, were it not supported by concurring observations. On the second a­batement I rose, and lighting a candle, looked on my watch, and [Page 14] found it to be 15' after 4. The shock then was not quite over, but the windows continued rattling for about a minute longer, as near as I can remember; for the shock went off very gradually. As soon as I had looked on the watch, I went directly to the clock, which was in another chamber, that I might see whether that agreed with the watch; and found that it was stop'd at 4 hours 11' 35". It's stopping, however, was not, immediately, owing to the violence of the shock, though several clocks, and watches too, at Boston are said to have been stop'd by it; but to the fol­lowing accident. Having some time before used a pretty long glass tube, in a particular experiment, I had shut it up in the clock-case for security; and this tube, being overthrown by the earthquake, lodged against the pendulum, and stop'd it's motion. By this accident, the beginning of the earthquake, I conceive, is determined with all the exactness that can be desired; for, so far as I can learn, the first shake was violent enough to overset so tall, slender a body, and standing in a position so near a per­pendicular, as that tube; and it was impossible for the pendulum to make one oscillation, after the tube had struck against it. Now from the time when the clock stop'd, to my looking on the watch, it was about 3' [...]; and the jarring was not quite over, till about a minute after this: So that I think I speak within bounds, when I say, that this shock with us lasted at least 4'. In other places, it's duration might possibly be different. I observe

Thirdly, as to the course of this earthquake, that it seems to have been nearly from N. W. to S. E. I was informed a few minutes after the shock, by a person who was upon the common in this town at the time, that the noise began about the N. W, and came on from thence, and pass'd away toward the S.E; and other accounts, which I have since met with, agree with this. Those who were in such clear, open places could make the best judge­ment in this matter; for such as were within doors, or surround­ed with buildings, might easily be misled by the various reflecti­ons of the sound. I am induced to give the greater credit to this information, by what I observed my self. For the key be­fo [...]e spoken of; as thrown from off a shelf in my house, was found at a place on the floor, which bore very near N. W. of [Page 15] the place from which it fell; though the situation of it before it's fall was such, that it might have been thrown in several other directions as well as that, had the course of the earthquake been different. ^f

[Page 16]Having mad [...] the observations propos'd, let us now attempt [Page 17] to trace out the causes of these great [...]. ^g

That the agents, which are able to produce affects so extra­ordinary as those before recited; which can ha [...]ve up such [...]nor­mous masses of matter, and put into the most vehement commo­tion vast tracts of land and sea, of many hundred miles in ex­tent;—that the agents, I say, which can do all this, and more, must be very powerful, will not admit of a doubt. Now we know of nothing in nature more powerful: than the particles of certain bodies converted into vapor by the action of fire. Fire then, and proper materials for it to act upon, it is probable, are the principal agents in this affair. And what greatly strengthens the probability is, an observation before-mentioned that those countries, which have burning mountains, are most subject to earthquakes; and that these mountains rage with uncommon fu [...]y, about the time when the circumjacent countries are torn with convul [...]ions;—an argument this, that the eruptions of such mo [...]n­tains, and earthquakes, are owing to one and the same cause. But we must be more particular.

[Page 18]1. The earth is not solid throughout, but contains within it many large holes, pits and caverns; as is agreed by all Natural Historians. There are very probably also long, crooked, une­qual passages, which run winding through a great extent of earth, and form a communication between very distant regions. ^h Some [Page 19] of these cavities are dry, and contain nothing but air, or the fumes of fermenting minerals; in others, there are currents of water.

2. This globe is a very heterogeneous body. Besides the two grand divisions of it into solid and fluid parts, each of these is again divisible into an indefinite number of others. Although our knowledge of the earth reaches but a little way below it's surface, yet so far as we have penetrated, it appears to be a com­pages of a vast variety of solid substances, ranged in a manner which to us seems to have not much of regularity in it. Here we find earths, stones, salts, sulphurs, minerals, metals, &c. and a great number of inferior species under each of these general heads, blended and intermingled with each other. Many of these are combustible, or of a texture proper to be turned by fire into flame and vapor. And besides the pure elementary wa­ter, if there be any such, the aqueous parts of the globe receive [Page 20] peculiar tinctures from the beds and veins through which they run; so that perhaps there may be almost as many sorts of wa­ters, as there are of solid substances. Thus, some waters are charged with sulphur [...]ous particles; some, with particles of iron; and others, with those of other minerals. And the [...]ubterrane­ous rivers and streams, thus impregnated with different particles, may, by their confluence, produce an almost infinite variety of mixtures in the earth. Probably, this promi [...]cuous disposition of materials, in the bowels of the earth, may be necessary to the growth of bodies in it; for in the judgement of some of the most eminent philosophers, particularly the excellent Mr. BOYLE, even the harde [...]t, inorganized bodies, as stones, metals, &c. do, in their proper way, grow within the earth, as truly as vegetables grow on it's surface, or animals in their parent animals. And to the same [...]nd seems to conduce.

3. The heat within the bowels of the earth. Heat, it is well known, is a grand agent in most natural productions; and the inner parts of the earth are sufficiently furnished with it. Some parts indeed, as the vulcanos, are actually on fire and burn; but there is, moreover, an heat without flame, diffused through the interior regions of the earth. This is evident from the instance of hot springs, and from the warmth which is always found at great depths, as in the bottoms of mines.

4. There seems to be an inexhaustible source of this heat in the attractive powers, which Sir ISAAC NEWTON has shewn to belong to the particles of matter. For, heat consisting in a p [...] ­culiar kind of intestine motion of the parts of bodies; whatever tends to produce this motion in bo [...]es, will cause them to grow hot. Now such a motion may be produced, by the particles of different bodies rushing together, in virtue of their attractive powers; of which that great man has given a very copious col­lection of instances in the 31st Question at the end of his Op­ticks, whither I must refer you. In some of them, not only a very sudden and violent heat, but an actual flame, is produ­ced, by the bare mixing of two cold bodies together; and that, even without the presence of the air, which we find absolutely necessary to our culinary fires. So in a remarkable experiment, (first made, I think, by Dr. SLARE) when a certain ‘compound [Page 21] spirit of nitr [...] is poured on half it's weight of any ponderous oil of vegetable or animal substances, the liquors grow so very hot in mixing, as presently to send up a burning flame.’ ⁹ At the first trial, so small a quantity, as ‘a drachm of this spirit, being poured upon half a drachm of such oil, in vacu [...], to see what effect would ensue; the mixture in the twinkling of an eye made a flash like gun-powder, and blew up the exhausted receiver, whose diameter was six inches, and depth above eight; all who were present being astonished at the unexpected event.’ There is also so strong an attraction between iron and sulphur, that 'even the gross body of sulphur powder'd,' con­tinues Sir ISAAC, ‘and with an equal weight of iron filings and a little water made into paste, in a few hours grows too hot to be touch'd, and emits a flame. And by these experiments compared with the great quantity of sulphur with which the earth abounds, and the warmth of the interior parts of the earth, and hot springs, and burning mountains, and with damps, mineral coruscations, &c. we may learn that sulphureous steams abound in the bowels of the earth, and ferment with minerals, and sometimes take fire with a sudden coruscation and explosion.’ But to set this curious doctrine in it's full light, it would be necessary to repeat that whole Question; which indeed highly deserves it, would the time permit. For it would then appear, that there is a very great variety of bodies, which being mixed together, produce so strong an effervescence, as to emit inflammable fumes. Thus, to mention one instance more, when iron is dissolving in a mixture of oil of vitriol and common water, there instantly arises a great heat and violent ebullition, with fumes copiously exhaling; which are so very inflammable, that, being set on fire, they go off at once like a gun, with a great explosion. Having thus seen what a perpetual source of heat there is in these powerful, active principles, con­tinu [...]lly [Page 22] operating within the bowels of the earth; let us next inquire, what effects may be expected from it. Therefore

5. It is a known property of heat to expand bodies, to rarefy them, and enlarge their dimensions; and, when raised to an high­er degree, to separate their parts, and make them fly from each other; as in some measure appears already from the instances mentioned under the foregoing article. This effect heat has upon solid as well as fluid bodies;—upon the hardest, as well as the soft­est. It is observable here, that such particles as cohere by the strongest attraction, do most forcibly repel one another, when they are once separated by heat. And when the heat is intense, and the particles of the heated body are prevented from flying away, till they become thoroughly hot; it will require very strong vessels to [...] their b [...]r [...]ing forth with a violent explo­sion. Thus, a single drop of common water, inclosed in a glass bubble, and laid upon the fire: as soon as it become hot, will burst the bubble, with a report sca [...] inferior to that of a pistol. And water in larger quantities has been heated to that degree, as to rend in sander very strong vessels of [...], in which it has been endeavour [...]d to be confined. What the [...] then would be, of a great body of water's suddenly making it's way into a flaming cavern, whose sulphur [...]ou [...] or [...] fires are not extinguished but in [...]ag [...]d by water; and of it's being there, almost instantaneously, converted into vapor; your own imaginations may easily represent to you. This, it is very likely, has some­times been the case with respect to those famous vulcanos, AEtna and Vesuvio; both which border on the sea. You see here what water may do; but there are many other bodies, which cohere more strongly, as sulphur and nitre, for example, whose vapor is still more powerful than that of water. This is evident from the composition of gun-powder; a very small quantity of which, when turned into vapor, every one knows, is able to remove any obstacle that opposes it's expansion, and to burst the firmest rocks. The paste abovementioned, made of powdered sulphur and iron filings, if put a few feet under ground, will by degrees cause the earth over it to heave and crack, to let out the flame; thus making an artificial earthquake. And therefore, if a water, [Page 23] saturated with sulphureous particles, should in it's passage under ground soak into a large bed of iron ore, or a strong c [...]alybeate water into a bed of sulphur; the mixture would doubtless per­for [...] in great, what this experiment does in miniature. A vitri­oli [...] water mixing with iron, if in sufficient quantities, would be followed with the like effect. But no mixture of this nature appears so surprizing as Dr. SLARE'S, which did not require so much as the presence of the air to inkindle it, From this small mixture, which was but one drachm and an half, a force was generated in an instant, by the mutual collision of those active liquors, far exceeding the weight of the atmos­phere that pressed down the receiver; which in that experiment amounted to about 420 pounds. I say, far exceeding; for the receiver was not barely raised, but 'with a much greater force blown up,' as Dr. SLARE expresses it. We have no right indeed, that I know of, to suppose all the same sorts of bodies, both solid and fluid, in the bowels of the earth, as chemistry has furnished us with; but several things induce us to believe, that in those dark recesses, impenetrable as they are to mortal eyes, bodies are prepared, by a kind of natural chemistry, which very much resemble many of our chemical preparations, and are pos­sessed of the same essential properties. To be sure, there are not wanting, in those lower regions, all the degrees of heat, which a Chemist could desire for any of his processes. If then two bodies, of the like nature as the spirit and oil used in this experiment, should be mingled together in due quantity, though in the closest subterraneous vault, which neither contained any genuine air, nor could admit any; I need not say, that an earth­quake must be the consequence.

You have now, I suppose, before you the general causes of earthquakes. You have seen that there are in the bowels of the earth inflammable materials, of various kinds, and in large quantities; some in the form of solid or liquid bodies, and others in that of exhalations and vapors; that there are also powerful principles constantly at work, which are capable of inkindling these materials into an actual flame; and that the vapor generated from such flame will endeavour to expand it self on all sides [Page 24] with immense force. If now these inflammable vapors be p [...]nt up in close caverns, so as to find no vent till they are collected in a large quantity; so soon as they take fire in any part, the flame will spread itself, wherever it meets with materials to con­vey it, with as great rapidity, perhaps, as it does in a train of gun­powder; and the vapors produced from hence will rush along through the subterraneous grottos, as they are able to find or force for themselves a passage; and by heaving up the earth that lies over them, will make that kind of progressive swell or un­dulation, in which we have supposed earthquakes commonly to consist; and will at length burst the caverns with a great shaking of the earth, as in springing a mine; and so discharge themselves into the open air. ¹⁰ These vapors may possibly sometimes in­fect [Page 25] the air, and bring on pestilential distempers, which have been said to be consequent upon great earthquakes. Not that [Page 26] I can give credit to all the reports of this sort, which have been handed about; many of them having been propagated by writers of an astrological turn, who have been as ready to attribute distempers to the configurations of the planets, and to the ap­pearance of comets, as to earthquakes.

By this time, enough has been said, I should think, to con­vince you, that the earth contains within itself the seeds of earth­quakes in great abundance. And all these things being consi­dered, it may seem rather a wonder that we have no more earth­quakes, than that we have so many. The causes of earthquakes are incessantly at work; and although it may require a course of years ^bb to ripen the proper materials to that pitch, as [Page 27] that they can force for themselves a passage thro' the earth; yet it is reasonable to expect, that they will from time to time be collected in such quantities, and ferment to such degrees, as to make these explosions unavoidable. As therefore our globe has been subject to such concussions from the earliest accounts of an­tiquity, we have no room to doubt but that it will continue to be so, as long as the present frame of nature subsists. For this we may be assured of, that though that imprisoned vapor be dis­charged into the open air, which, by its struggles to escape, has caused an earthquake; yet the fermenting minerals, from which it was generated, will be continually supplying new quantities of the same; and even those very minerals may from time to time be re-produced, as they are consumed; as was before ob­served. Thus we see, that in the very structure and constitution of this globe, provision has been made to continue these agitations of it, at proper intervals of time, during the whole period of it's existence in it's present form; and that in every climate, from the equator to the pole. This suggests a reflection, with which I shall close the present discourse. It is this: That

Though these explosions, and consequent concussions of the earth, have indeed occasioned most terrible desolations, and in this light may justly be regarded as the tokens of an incensed DEITY; yet it can by no means be concluded from hence, that they are not of real and standing advantage to the globe in ge­neral. Multitudes, it is true, have at different times suffered by them; multitudes have been destroyed by them; but much greater multitudes may have been every day benefited by them. The all-wise CREATOR could not but foresee all the effects of all the powers he implanted in matter; and, as we find in innumerable in­ [...]ances (and the more we know of his works, the more such in­ [...]ances we discover) that he has established such laws for the go­vernment of the world, as tend to promote the good of the [Page 28] whole, we may reasonably presume, that he has done it in this case as well as others. To me, at least, the argument on this side the question, drawn from the general analogy of nature, ap­pear [...] to have more force, than any that I have seen offered on the other. For there is nothing, however useful, however ne­cessary, but what is capable of producing, and in fact has produ­c [...]d, damage, in single in [...]ances. It were endless to particular­ize here; I shall therefore only mention one or two things by way of specimen. The power of gravity,—a power of such indispensable importance, that without it the system of nature could not subsist a moment, has yet proved the destruction of multitudes. The wind, so necessary for the purposes of navi­gation, as well as to purge the air, which would otherwise [...]ag­nate and pu [...]refy,—how often has it risen to [...]uch a pitch, as to overthrow houses, and wre [...]k vessels? by which means thou­sands have perished. Even thunder and lightning, which, next to earthquakes, are the most terrible phaenomena of nature, are yet universally allowed to be necessary to free the atmosphere from a certain unwholsome [...]ultriness, which often infects it. Other instances of the like sort I leave to your own reflections: and would rather observe, that the world is governed by general laws; and general laws must, from the nature of them, be liable sometimes to do hurt. However, laws of this sort are suffici­ently vindicated, not only as wise, but as good, if upon the whole they produce a maximum of good; (to borrow an expression from the Mathematicians;) and this, it is in the highest degree pro­bable, all the laws of nature do. It may be added, that as in the animal body, the evacuations, which are of ab [...]olute necessity to maintain life and health, do yet sometimes run to such extremes as to prove mortal; so in like manner, these explosions of sub­terraneous vapor, whose effects have sometimes been so fatal, may, notwithstanding this, be highly conducive, and even indis­pensably necessary, to the good of this globe in general. The explosions themselves, as well as the laws, in consequence of which they are produced, may be necessary on various accounts; [Page 29] and particularly to the carrying on the more secret and noble works of nature within the entrails of the earth. ^cc Let me dilate a little on this matter.

By the incessant action of gravity and other attractive powers, and by the perpetual consumption of fluids, the earth becomes, continually more and more hard, compact and dense. Now an openness or looseness of contexture, to a certain degree, in the earth, is necessary to carry on the operations of nature within it. So that on the supposition that mineral, metalline, and other subterraneous bodies grow within the earth, it should seem that the earth must become gradually less and less fit for the produc­tion of them. Since then the direct, immediate, and most general effect of earthquakes is, by shaking to loosen and disunite the parts of the earth, and to open it's pores, it seems agreeable to reason to infer, that this is the end primarily aimed at in these concussions. But you will take notice, that I speak here only, of physical or natural ends. For though I make no doubt, that the laws of nature were established, and that the operations of nature are conducted, with a view, ultimately, to moral purposes; and that there is the most perfect coincidence, at all times, be­tween GOD's government of the natural and of the moral world; yet it would be improper for me to enter into these di [...] ­quisitions at this time, since my province limits me to consider th [...] subject, only in the relation which it bears to natural philosophy. It is in the physical sense alone that I say, the disjoining the parts of the earth, and opening it's pores, may be the end primarily aimed at in earthquakes, as such mutations in the earth may from time to time become necessary to the production of subterraneous [Page 30] bodies; and perhaps this end could not be effectually answered by less forcible methods. This point may receive some light, if not proof, from the operations of agriculture. We find it necessary, by ploughing, digging, &c. to break the clods of the ground, to comminute and even pulverize it, in order to fit it for the purposes of vegetation; and we find it necessary to renew these labors every year. Now the use and tendency of these artificial operations may bear some analogy to those of the greater operations of nature, which we are speaking of. And indeed, it is not in the least degree improbable, that such a loosening of the parts of the earth may promote even the growth of vege­tables on it's surface, as well as of minerals in it's bowels; it being now well known, that all vegetables, the smaller as well as the larger, shoot some fibres of their roots to vastly greater depths, than those to which any of our instruments of tillage ever penetrate. This, it is, likely, may be one reason of the wonder­ful fertility, for which AEtna and Vesuvio have been so gene­rally and so highly celebrated. Again; it may be necessary now and then, to have such subterraneous vapors, as are gene­rated by fermentation, discharged up into the air; as their con­tinuance below, in the caverns of the earth, might be an impedi­ment to those important processes which are there carrying on. But those very vapors, which might obstruct some sorts of natural processes, while below the surface of the earth, may as much advance others, when above it. We know that in many cases of the fermentation of bodies, especially of such dense ones as salts and minerals, air is plentifully absorbed; and that in many others, it is as plentifully generated: So that great part of the exhala­tions thrown out by earthquakes may be true, permanent air, and designed to recruit what has been absorbed by bodies here on the surface. And perhaps the grounds, on which the great NEW­TON founded his ‘suspicion, ^dd that the finest, the most subtile, and most spirituous parts of our air, and those which are most necessary to maintain the life of all things, come chiefly from the comets’; may equally support another suspicion, that some [Page 31] such particles of air may be derived also from subterraneous eruptions. For among the almost infinite variety of particles which are thrown out of the earth in these eruptions, it is most likely, that if some are noxious, others will be salutary. It may also be necessary from time to time to have the subterrane­ous streams diverted from their former courses into new ones: partly, that different places in the lower regions may be watered by them; and partly, that the waters themselves, by passing through different beds or chanels, may alter their properties, ^ee and convey new tinctures to different places.

But however these things may be; whether all the foregoing conjectures be well founded, or not: If these explosions and con­cussions be, as it is next to certain that they are, the necessary and inevitable consequences of such laws of nature, and such powers in matter, as our globe could not well subsist without; this ought to silence all the complaints of those who suffer either loss or terror by them; as well as all the objections, which men of [...]c [...]ptical minds have been disposed to make, upon this head, to the order of Providence. It ought, in reason, to do this, though we should never be able to point out all the particular advantages resulting from them. For, it is plain, they may be beneficial in a thousand other ways, than we, short-sighted mor­tals, may pretend to guess at.

To sum up all in a word. This is a MIX'D state; in which there is such a variety of purposes, natural as well as moral, in prosecution at the same time, that there may be nothing, per­haps, in the material world, that is simply and absolutely evil;—nothing, but what, under the direction of infinite wisdom, power and beneficence, is, in some or other of it's consequences, pro­ductive of an over-balance of good:

Upon the whole. How 'wonderful in counsel,' how ‘ex­cellent in working’ is that BEING, who can bring good out of the greatest evils; and can answer intentions, the most widely differing, by one and the same dispensation of His providence!