Abbildungen der Seite

area in acres, rods and perches. The gauger is instructed how to find the capacities or solid contents of all kinds of vessels, in barrels, gallons, bushels, Ste. And the meas-urer is furnished with rules for finding the areas and con. tents of superfices and solids, and casting up all manner of workmanship. All thes nd many more useful arts, too many to be enumerated here, wholly depend upon the aforesaid sciences, viz. arithmetic and geometry. .

This science is descended from the infancy of the world, the inventors of which were the first propagators of human kind, as Adam, Noah, Abraham, Moses, and divers others.

There has not been any science so much esteemed/and honored as this of the mathematics, nor with so math industry and vigilance become the care of great/men, and 13-bored in by the potentates of the world, Viz- emPerQ", kings, princes, &c. / ' \

Mathematical demonstrations. are 310836 of as much 01' more use, than that commonly learned at schools, serving to a. just formation of the mind, enlarging its capacity, and strengthening it so, as to render the same capable of exact reasoning, and discerning truth from falshood in all occur

rences, even subjects not mathematical. For which reason

it is said, the Egyptians, Persians, and Lacedemonians, seldom elected any new kings, but such as had some knowlege in the mathematics, imagining those who had not, men of imperfect judgments, and unfit to rule and govern.

Though Plato’s censure, that those who did not understand the 117th proposition of the 18th book, of Euclidis Elements, ought not to be ranked amongst rational creatures, was unreasonable and unjust; yet to give a man the character of universal learning, who is destitute of a competent knowlege in the mathematics, is-no less so.

The usefulness of some particular parts of the mathematics in the common affairs of human life, has rendered some knowlege of them very necessary to a great part of mankind, and very convenient to all the rest that are any way conversant beyond the limits of their own particular call“ mgs.

Those whom necessity has obliged to get their bread by manual industry, where some degree of art is required to go along with it, and who have had some insight into these studies, have very often found advantages from them sufli— cient to reward the pains they were at in acquiring them. And whatever may have bee .puted to some other stu— dies, under the notion of insignificancy and loss of time, yet these, I believe, ncver caused repentance in any, except it was for their remissncss in the prosecution of them.

Philosophers do generally aflirm, that human knowlegc

, 10 be most excellent, which is conversant amongst the most

excellent things. What science then can there be, m0r¢ noblc, more excellent, more useful for men, more admira-bly high flml demonstrative, than this of the mathematics.

I Shall Conclmie with what Plato says, lib. 7. of his Re— Public, with regard lb the excellence and usefulness ofgeometry, being to this purpsse 1_

“ Dear Friend...-You 586 thin that mathematics are ngcessary, because by the exactness of the method, we get r habit of using our minds to the best advantage : and it is remarkable, that all men being capable by nature to reason and understand the sciences; the less» acute, by studying this, thoughiis'e'le'ssi'fiiithemjin every other respect, will gain this advantage, that their minds will be improved in reasoning aright ; for no study employs it more, nor makes it susceptible of attention so much; and these who we find .have a mind worth cultivating, ought to apply themselves to this study.” ‘

From the Pennsylvania. Gazette, No. 4170, Dec, 15, 1737.

THE late earthquake felt here, and probably in all the neighboring provinces, have made many people desirous to know what may be the natural cause of such violent concussions, we shall endeavor to gratify their curiosity ‘by giving them the various. opinions of the learned on that head. ' ' ‘

L ni_cni‘____. . n__-o-.—__ .

Here naturalists are divided. Some ascribe them to water, others to fire, and others/to air: ,and all of them with some appearance of reason. To conceive which, it is to be observed, that the earth every where abounds in huge subterraneous caverns, veins and canals, particularly about the roots of mountains: that of these cavities, veins, $tc. some are full of water, whence are composed gulphs, abysses, springs, rivulets; and others full of exhalations; and that some parts of the earth are replete with nitre, sulphur, bitumen, vitriol, &c.

This premised, 1. The earth itself may sometimes be the cause of its own shaking; when the roots or basis of some large mass being dissolved, or worn away by a fluid underneath, it sinks into the same; and with its weight, occa— sions a tremor of the adjacent parts ; produces a noise, and frequently an inundation of water.

2. The subterraneous waters may occasion earthquakes, by their overflowing, cutting out new courses, 81c. Add, that the water being heated and rarefied by the subterraneous fires, may emit fumes, blasts, 8:0. which by their action, either on the water or immediately on the earth itself, may occasiQngl‘Cat SUCCIISSlOI‘lS

3, The air may be the cause of earthquakes: for the air being a collection of fumes and vapors 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 endeavors to escape, may shake the earth: hence there arise 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 vapors; and as this aura, or spirit, from the different matter and composition whereof arise sulphur, bitumen, and other inflammable matters ; takes fire, either from some other fire it meets wit'nal, 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 this sulphur, in the former, is fired in the air; and in the latter under ground. Which is a notion that Pliny had long before him : Quidenim, says he, alz'ud est in term tremor, guam in nube tanitru .9

This he thinks abundantly indicated by the same sulphurous smell being found in any thing burnt with lightning ; and in the waters, 8m. 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 vapors 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 vapors dispersed through it, in; force enough to shake our houses; and why may not there ‘as 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 vapor above us, is in much larger quantities under ground.

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

Add, that the pyrites alone, of all the known minerals, yields this inflammable vapor, 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 volcanos, is only an argument of the long duration and vehemence of those fires; possibly, the pyrites of the volcanos, 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 one reason why England is so little troubled with earthquakes; and Italy, and almost all round the Mediterranean sea, so

very much: though another reason is, the paucity of py

rites 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. pose 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 endeavors to shew, 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. ’

To this pur— ‘

« ZurückWeiter »