« AnteriorContinuar »
Pandere tenuïculos; et flabra ferentia venti
Difce, quod ingenium, mores, ftudiumque popellos
Res, advorte, ratas jura inviolata propagant,
Perque iftas, merus INSTINCTUS quas præbeat, artes
ART. LI. A Treatise on ELECTRICITY: wherein its various phoenomena are accounted for, and the cause of attraction and gravitation of folids, affigned, &c. By Francis Penrofe, furgeon at Bicefter. 8vo. Is. Owen.
IN this effay, mr. Penrose endeavours to fhew, how, and from whence the electrical fire and force are produced; and then makes fome obfervations to ascertain how it acts upon the animal frame, and it what disorders it is likely to be of benefit.
As to the cause of electricity in any body, he thinks it wholly owing to the friction or attrition of the air furrounding that body, when put in motion, and by no means to any effluvia proceeding from the body itself, as is the commonly received opinion. His reasons for fo thinking are, that air, light, and fire, being of the fame substance or effence, an attrition, dividing or breaking air, produces light, and, if that action is ftill encreafed, it produces fire. To prove this, he brings the follow experiments, viz. if you flide a wax-thread, or fmall rope, through your fingers, it will burn them. So likewife fire is produced,
by rubbing two hard bodies together, as two sticks, a coachwheel, a cable, &c. From the fame principle, viz. the violent attrition of the particles of air, he accounts for the firey flakes, balls, &c. feen at fea in tempeftuous weather, and called, Helena, Caftor and Pollux.
He brings feveral other experiments, all tending to prove, that heat or fire is wholly owing to friction or violent motion: and in order to make it appear, that air itself is of the fame fubftance with fire, he obferves, that fire cannot fubfift without air, and in porportion of air forced into the fire, in fuch proportion will be the force of the fire. Again, fire can only act on the outfide of bodies next the air; for even the most inflammable bodies can only catch fire on their outermoft furface and fire in action, if immerged in a body of the most inflammable matter, will be fo far from kindling the inflammable body, that itself will be extinguished.
These experiments, he thinks, prove, that, whenever air is fufficiently divided or broken to pieces, light is produced: fo that the light or heat in electricity is no other than what may be produced feveral other ways. For the air being violently rubbed or ground to pieces between your hand and the glafs globe, whirled brifkly about, it appears in the form of light, expanded or fent off from the glafs globe in the fame manner as light from a candle; which emiffion is continually fupplyed by the common air preffing in between the rays of light, emitted from the glass ball. That this is the method by which it acts, feems very clear; for you may not only hear the hiffing noife of the air preffing towards the globe, but alfo plainly feel it with your hand.
This rarefaction of the air produced by a violent motion, and the preffing in of grofs air to fupply its place, gives a very clear idea, according to our author, in what manner the fun is fupported, how this terraqueous globe and the rest of the planets are made to move, and continued in motion; and alfo what is the cause of the attraction of the fun, earth, moon, and the reft of the planets. Thus our author accounts for all the phænomena of nature, as attraction, gravitation, and even the folidity of bodies, by the preffure of the atmosphere.
What is called the attraction of the earth, continues he, feems to be performed in the fame manner as that of the glass globe in electricity: the explaining of which will give us a clear idea by what means heavy bodies are forced towards the terraqueous globe. This he does from mr. Haukee,
Haukfbee, who fays, "If by the heat and rarefaction, confequent upon the attrition, the medium contiguous to the glafs be made fpecifically lighter; then of course, to keep up the balance, the remoter air, which is denser, must prefs in towards the tube, and so carry away (in the torrent) the little bodies lying in its way, thither allo. The various irregularities in the excitation, or the emiffion and difcharge of the electrical matter, or light, from the tube, (which will be followed by proportional irregularities, in the motion and tendency of the denfer air, towards the glass globe, by the hydroftatical laws) may be fufficient to account for the various uncertain motions of the little bodies carried towards the glafs globe."
Here our author obferves, that, as this account of mr. Haukfbee's is fo very clear, it seems ftrange that he should allow the power of attraction to matter, as in fome places he does.
After this he explains the gravitation of bodies towards the earth, from the fame principles. The fun-beams near the furface of the earth, being reflected by the terraqueous globe, muft by that means be in a greater quantity there, than at a distance from it; and fo divide, rarify, and expand the air next the furface, which rarifyed or divided air is forced off from the earth on all fides, by the preffing in of the air from above, which muft of confequence drive every thing before it towards the earth. Hence it appears, that the caufe of bodies defcending towards the earth is not from any property either of the earth, or of the descending bodies, but entirely to their being forced towards it, by the furrounded air, in its faid motion.
Mr. Haukfbee's reafoning, in regard to what is called the attractive and repulfive power of electricity, is certainly very juft; but our author's application, of it, appears to us forced, and carried farther than the thing will bear. That the rarefaction of the air near the furface of the earth, and the preffing in of the more denfe air, may be the cause of winds, we allow; but can by no means admit this to be the cause of gravitation and the folidity of bodies.
Mr. Penrofe, in the last place, briefly hints at the disorders in which electrical operations are likely to do good or harm. In fevers, and inflammations of all kinds, he thinks the worst and moft pernicious confequences may be expected from the use of electricity. But, on the contrary, as the nerves act by a fubtile fluid paffing thro' them, and, by reafon of the clofenefs of their pores, admit no fluid whose
particles are much larger than thofe of light; the confequence of fuch a make muft often be obftructions; which, as the light in electricity is forced thro' our bodies and nerves, may be broken and removed by its power: of which there are many inftances, especially in palfies and other disorders of the nerves.
ART. LII. Obfervations on Tacitus. In which his character, as a writer and an hiftorian, is impartially confidered, and compared with that of Livy. By the reverend Thomas Hunter, vicar of Garítang in Lancashire. 8vo. 4s. bound. Manby.
E fhall not detain our readers with a long account of this performance, but leave them to judge of its author's critical talents from a few extracts. The whole is divided into two parts. In the first part of which mr. Hunter endeavours to make it appear, that Tacitus is a vain, ignorant, credulous writer, void of judgment and candour; and brings a variety of paffages from him in order to fupport this heavy charge.
He introduces his work in the following manner: To vanity, fays he, may we not afcribe his tedious digreffions and frequent excurfions into remote ages and distant nations, which have little or no connection with the Roman ftory, or the times, which he proposes as the subject of his writings? I remember not to have met with any objection to Tacitus on this account, which I am the more furprised at, as the affectation here is fo very apparent. He lets flip no opportunity, but catches at any little hint, and makes forced connections to run back into antiquity, to give his work the more venerable air, and at the same time difplay his own deep erudition.'
Having confidered Tacitus's vanity and affectation of dabbling in antiquity, as he calls it, our author proceeds to examine his descriptions; and these, he tells us, are overlaboured, unnatural, and fometimes even mean. He defcribes, fays he, not as things really are, but gives them undue proportions, and annexes unnatural circumstances, to ftrike and amaze the more. He leaves nothing to the reader to imagine. All is enlarged and magnified even beyond the bounds of nature and decency. Whether he defcribes the works of art, or the products of nature, actions, paffions, or perfons, they must have fomething strange or great to command more notice, and raise the merit of our
author's writings.—If Tacitus is any where happy in his defcription, it is in the difplay of guilty greatnefs. Luxury refined and high-flavoured, royal debauch, imperial whoredom, feem as much adapted to his pen, as Livy is charmed with the virtuous part, with the amiable glory of the temperate Scipio, or the illuftrious poverty of the rural dictator. Never writer had a happier pen at defcribing wickednefs than our author. It is the most natural part of his writings. Were we to give room to the fufpicions we fhall have presently occafion to blame in Tacitus we should fay he might have been an advifer and an actor in every villainous defign, and a party in every lewd scene he reprefents. Sir H. Savil has more than once charged our author with negligence in his descriptions; but I rather think his fault or his misfortune was ignorance.'
He tells us, that Tacitus is perpetually endeavouring to affect his reader with indignation, pity, or furprize. But then, fays he, his ftudy to affect you appears fo plain, that it defeats his defign. His aim is to make himself the most confpicuous perfonage of the ftory; and fo far he gains his aim, that you never lofe fight of him but then it fares with him, as with an affected beauty, who, not content with the charms which nature has given her, calls in the help of art to catch all eyes, and lofes admirers by too apparent a paffion to gain them.
To this vanity of our author to display himself and amaze his reader, I afcribe his fondness for the miraculous, his mixing natural with civil hiftory, his credulity and falfhood. As his defcriptions are extraordinary, and his paffions extravagant; fo his lies are egregious ones, and his prodigies moft prodigious.'
After this he proceeds to fhew, that there is a great deal of meanness in the writings of Tacitus ; and then obferves, that there is one quality in him, for which no fufficient apology has been, or can be made; and which renders him perhaps the most disagreeable writer that a reader of any humanity can perufe. 'Tis that perpetual malignity, fays he, and ill-nature which difpofes him upon all occafions to cenfure, blacken and defame, and to give the worst meaning to actions capable of a kinder interpretation and a more candid sense.'
He tells us, there is very little in Tacitus that comes under the character of pure hiftory, and that his writings confift of conjecture, reflection, differtation, debate, eloquence, politicks, proverbs, antiquity, affectation, fatire, fneer, far