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Dr. Milhe's zeal against infidels and infidelity is so great, that he could not avoid a sort of a back-hand stroke at Mr. Hume, and his manner of quitting the world. He will boast to the last moments (says the Preacher) of a pretended strength of mind which shall flatter his vanity; incline to feem superior to vulgar errors, to brave the authority of heaven, and view the uncertainty of an hereafter with a fixed and tranquil eye ; leave to the spectators the dreadful pleasure of a witticism at the expence of his eternal salvation, and talk jocularly of Styx and Charon.' (Vid. Serm. On the Deceitfulness of Sin, p. 216. comp. with Dr. Adam Smith's Letter to William Strahan, Esq; affixed to Mr. Hume's Life.)

We shall produce one specimen more of the Preacher's zeal ; and it will serve as a farther specimen of his happy talent at antithesis. • Would you take those for your models whose names offer themselves with horror to remembrance, the Vaninis, the Spinosas, the Woolstons, the Voltaires ? or the — Now, gentle Reader, dost thou not expect fome modern champion of the Christian church to figure in the contraft ? - the Pascals, the Boyles, the Newtons, the Lockes, the Lytteltons ? --Thou art mistaken! Dr. Milne opposes to the Spinosas, the Woolstons and the Voltaires – the Abrahams, the Josephs, the Jobs, the Elijahs, the Daniels, the apoftolical men, who shone as lights in the world. Maintain (says he) if you can this parallel.' It is not our business, nor the bufiness of any one's but the Doctor's, to maintain such a parallel ; and it will require more ingenuity than he is poffeffed of to maintain it with any grace.

Dr. Milne, and the partial friends who perfuaded him to commit his compositions to the inspection of the public,' will certainly accuse us of great severity and ill-nature in treating him with such freedom as we have in the preceding remarks. But when we think we have discharged an honest, though harsh and ungrateful duty; and when we know that we have done it without the fightest personal prejudice against the Author, or even the most distant knowledge of the man, any farther than he hath made himself known to us by his publications, we shah acquit ourselves to our own consciences, and consider every Splenetic reflection from partiality and disappointment as a thing of course. We consider Dr. Milne as a most dangerous and corrupt model for our young divines-who are too easily captivated by the charms of a false and specious eloquence, to the neglect, and perhaps the contempt, of those words of truth and Soberness, which aim more at the conviction of the judgment than at the inflammation of the passions; and gain by a calm and lasting effect, what they miss by sudden and violent emotions.



Art. IV. Principles of Ele&ricity, containing divers ner Theorems

and Experiments, together with an Analysis of the superior Advana Tages of high and pointed Conductors, &c. By Charles Viscount Mahon, F. R. S. 4to. 105, 6d. Boards. Elmlly. 1779. HOUGH the ingenious and noble Author of this per

formance professes to establish in it'the fundamental laws of Electricity;' the prefent is not an elementary treatise of that science. The reader is accordingly supposed to be acquainted with the common experiments, and the general properties of electricity, which have been already established by others.

The Author first treats of Electric Atmospheres; and endeavours to thew that they are constituted of the particles of air surrounding the electrified body. If, for instance, the body be positively electrified, he maintains that it will deposit, upon all the particles of air that surround it, and come successively in contact with it, a proportional part of its fuperabundant electricity : so that they will become likewise positively electrified, and form a positively electrified atmosphere *. The same reasoning is applied, mutatis mutandis, to negatively electrified bodies, and their negative atmospheres.

From this principle, and the observation that the density of an electrical atmosphere diminishes, in a certain ratio, as the diftance from the electrified body increases, as well as from other considerations, the Author undertakes to assign the cause, why an electrified body, to which a projecting point is affixed, parts with, or receives, electricity more readily than a smooth cylindrical or globular body :-Because the superabundant electricity of the body, which we will suppose to be positively electrified, and which, in all cases, tends to quit it, will, when a point is affixed to it, meet with less resistance to its escape ; as the point projects beyond the dense part of the electrical atmosphere of the body, into the rarer and, consequently, more unresisting part of that atmosphere. But the escape of the electric matter from any part of a smooth cylindrical body, pofitively electrified, is prevented or impeded; because every part of its surface is in contact with the densest part of its own strongly refifting electric atmosphere. The surface too of the point being extremely small, the less will be the resistance op

* We wonder that the Author should take no notice of those ob. fervations of Dr. Franklin, that seem to militate against this doctrine; particularly his experiment, in which a large eletrified cork ball, fixed to the end of a filk Aring, was whirled swiftly round a hundred times in the air, like a fling; without sustaining any sensible loss of electricity, after having passed through 800 yards of air. See his Experiments and Obfervations on Ele&ricity, ci Letter VI. Ff 2


posed to the escape of the fuperabundant electricity of the body, into that rare part of its electrical atmosphere into which the point projects.

Among other illustrations of this principle the Author produces the case of a pointed wire, placed between two round or prominent metallic bodies, with its point on a level with their surfaces. In this situation, when presented to an electrified body, it acts no longer as a point, or only in a very small degree : because the dense part of the electrical atmosphere of the two round bodies flows or is extended over it.

The Author's succeeding experiments Thew that an insulated smooth body, a cylindrical conductor for instance, immerged within the electrical atmosphere, but beyond the striking distance, of another body, which we shall suppose to be charged positively *, is, at one and the same time, in different parts of it, in a state of three-fold electricity,' The end next to the charged body acquires negative electricity; and the farther end becomes positively electrified : while a certain part of the body, somewhere between its two extremities, is in a natural, unelectrified, or neutral state: so that the two contrary electricities exactly counterbalance each other in that part. The Author on this occafion employs geometrical reasoning, as well as experiments, to determine the precise place of this un-electrified point, or rather line, in a cylinder or other given body; and to demonstrate that the density of electrical atmospheres is inversely as the square of the distance from the electrified body.

We scarce need to add, that if the body be not insulated, or have a communication with the earth, the whole of it will be in a negative state: a certain portion of its natural quantity of electricity being driven into the common mass, by the pressure, repulf:on, or other action, of the electric matter belonging to the charged prime conductor. The extenfive and fruitfui principle, on which this and the preceding effects depend, has frequently been explained or referred to in the course of our Journal ; particularly, and very lately, in our Review for December last, page 408; where it is noticed for the purpose of explaining the phenomena of the electrophorus. We take the more particuJar notice of it at present; as one of the Author's most remark. able observations on the subject of thunderstorms, and from which he draws some very striking, indeed formidable, conclufions, is founded upon it.

We allude to what the Author calls the electrical returning froke;' by means of which, he alleges that, in a thunderstorm,

* To avoid repetition, or circumlocution, we fall, throughout the remainder of this Article, constantly suppose the electrified body to be chasged with positive electricity,


the most fatal effects may be produced, even at a vas distance from the place where the lightning falls. This observation appears to be of so much importance, that we shall endeavour to give as clear an idea of the experiments on which it is founded, as can be conveyed by'us, without the use of plates : not confining ourselves to any particular experiment; but relating such material circumftances common to them all, as may best convey the Author's meaning in the fewest words.

We ought to premise that the Author used a very powerful machine, made by Mr. Nairne; the prime conductor of which (fix feet long, by one foot diameter) would generally, when the weather was favourable, ftrike into a brass ball connected with the earth, to the distance of eighteen inches, or more. In the following account this brass ball, which we shall call A, is supposed to be constantly placed at the striking distance; so that the prime conductor, the instant that it becomes fully charged, explodes into it.

Another large conductor, which we shall call the second conductor, is suspended, in a perfectly insulated state, farther from the prime conductor than the striking distance, but within its eleEirical atmosphere ;-at the diltance of six feet, for instance. A person standing on an insulating stool touches this second conductor very lightly with a finger of his right hand; while, with a finger of his left hand, he communicates with the earth, by touching very lightly a second brass ball fixed at the top of a metallic stand, on the floor, and which we shall call B.

While the prime conductor is receiving its electricity, sparks pass (at least if the distance becween the two conductors is not too great) from the second conductor to the insulated person's right hand; while similar and simultaneous sparks pass out from the finger of his left hand into the second metallic ball B, communicating with the earth. These sparks are part of the natural quantity of electric matter belonging to the second conductor, and to the insulated person ; driven from them, into the earth, through the ball B, and its stand, by the elastic preffure or action of the electrical atmosphere of the prime conductor. The second conductor and the insulated person are hereby reduced to a negative state.

At length however the prime conductor, having acquired its full charge, suddenly strikes into the ball, A, of the first metallic ftand, placed for that purpose at the striking distance of 17 or 18 inches The explofion being made, and the prime conductor suddenly robbed of its electric atmospåere, its pressure or action on the sea cond conductor, and on the insulated person, as suddenly ceases; and the latter instantly feels a smart returning stroke, though he has no direct or visible communication (except by the floor) either with the Ariking or struck body; and is placed at the dil


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tance of five or six feet from both of them. This returning stroke is evidently occasioned by the sudden re-entrance of the electric fire naturally belonging to his body and to the second conductor, which had before been expelled from them by the action of the charged prime conductor upon them; and which returns to its former place, the instant that action or elastic pressure ceases. The Author shews that there can be no reason to suppose that the electrical discharge from the prime conductor should, in this experiment, divide itself at the instant of the explofion, and go different ways į so as to strike the second conductor and insulated person in this manner, and at such a distance from it.

When the second conductor and the insulated person are placed in the denses part of the electrical atmosphere of the prime conductor, or just beyond the striking distance ; the effects are ftill more confiderable: the returning Aroke being extremely revere and pungent, and appearing confiderably sharper than even the main stroke itself, received directly from the prime conductor. This circumstance the Author alleges as an unan{werable proof that the effect which he calls the returning stroke was not produced by the main stroke being any wise divided at the time of the explofion, fince no effet can ever be greater than the cause by which it is immediately produced.'-Having taken the returning stroke eight or ten times one morning, he felt a confiderable degree of pain acrofs his chest during the whole evening, and a disagreeable sensation in his arms and wrists all the next day.

We come now to the application of this experiment, and of the doctrine deduced from it, to what passes in natural electricity, or during a thunderstorm; in which there is reason to expect similar effects, but on a larger scale :-a scale so large indeed, according to the Author's representation, that persons and animals may be destroyed, -and particular parts of buildings may be considerably damaged, by an electrical returning froke, occasioned even by some very diftant explosion from a thun, dercloud ;'- poffibly at the distance of a mile or more.

It is certainly easy to conceive that a charged extenfive thundercloud must be productive of effects similar to those produced by the Author's prime conductor. Like it, while it continues charged, it will, by the superinduced elastic eletrical preffure' of its atmosphere-to use the Author's own expression drive into the earth a part of the electric fluid naturally belong: ing to the bodies which are within the reach of its widely ex. tended atmosphere ; and which will therefore become negatively electrical. This portion too of their electric fire, as in the artificial experiments, will, on the explosion of the cloud, at a diffance, and the cessation of its action upon them, suddenly return


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