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for the excellent work he had dedicated to me ; but at the same time I informed him, that, sensible to the good wishes expressed in his Dedication, I should be ungrateful if I did not, for his own sake, with that he had entirely altered the style of it.' • M. Suhm's letters are much inferior to those of the Prince, and are so full of adulation, we had almost said adoration, that we wonder they did not draw a serious reprimand from his Highness, who indeed checks him frequently on this account. His affection was no doubt sincere and praise-worthy, but his expression of it is as ridiculous as the love ditty of a whining knight in romance, and is void of that fuber dignity which should characterise the friendship of a man of sense. His transports and extasies are so much in the superlative degree, and so repeatedly expressed, that we were quite cloyed and disgusted with them.
The subjects to which these letters are confined are not the most interesting and entertaining. They contain no political or historical anecdotes, and are remarkably filent concerning the Court of Berlin. This was prudent, considering the Prince's disagreeable fituation at that time. His Royal Highness, who entertained rather an unreasonable prejudice against the German, and in favour of the French language, had engaged M. Subm to translate Woli's metaphyfics, and to send him the translation, Cheet by sheet, inclosed in his letters. An account of the progress of this work, and a few general encomiums on Wolf, are all the information contained in the first thirty-fix letters; after which we find that M. Suhm was appointed by the Elector to fucored the Count de Linar as Envoy Extraordinary to the Court of Petersburgh. The remainder of the correspondence relates to certain fums of money which the Prince secretly borrowed from the Empress Anne Iwanowna of Rufia, and from the Duke of Courland, formerly Count Biron, her favourite. Among there leiters, there is one in which his Highness mentions his having been accused, to the King, of irreligion, and adds, “You know that an acculation of this kind is the last refuge of calumny; afier this, nothing further can be said. The King took fire; I kept myieli ciole ; my regiment did wonders; and their dexterity in handling their arms, a little four scattered on the foldiers heads, men above fix feet high, together with a great many recruics, were arguments more powerful than those of my accusers. Every thing is now quiet, and I hear nothing more about religion, my persecutors, or my regiment.' . On the Prince's accellion to the throne, one of his first cares was to persuade M. Subm to resign his connections with the Court of Dresden, and to fix at Berlin. The lacter complied with this cordial invitation, but, on his journey, died at Warsaw; and his last lester, dated from this city, is the dying man's Rr2
pathetic recommendation of his filter and his children to his royal friend. This letter is admirably written : it Aows immediately from the heart; and it gives us an affecting view of tbe sentiments of the Christian, the philosopher, the father, and the friend, in these awful circumstances; and affords a striking inftance of the vanity of our most probable schemes of worldly happineis.
This correspondence is followed by a few short letters from the King to the Countess de Samas, who was at the head of the Queen's bousehold, written between the years 1760 and 1763. They are pleasant trifles. We have attempted to translate one of them, which shews the King's mind to have been perfectly at ease amid the horrors of war, and superior to the influence of external circumstances.
Newsadt, November 11, 1760. "I am punctual in answering, and eager to oblige you. Persons of the same age agree wonderfully. I have given up suppers these four years, as incompatible with the business I am forced to carry on ; and, on marching days, my dinner is only a dish of chocolate. We have been running like madmen, quite elated with victory, to see whether we could drive the Austrians from Dresden; but they Jaughed at us from the tops of their mountains. I returned like a disappointed child, to hide my vexation in one of the most cursed villages of Saxony. We must now drive Messieurs Les Cercles out of Freyberg and Chemnitz, in order to get something to eat, and a place to sleep in.
· This is, I swear, such a dog's life, as no one, except Don Quixotte, ever led but myself. All this buitle, all this confufion, which seems to be without end, has made me such an old fellow, that you will hardly know me again. The hair on the right side of my head is grown quite grey; my teeth break, and fall out; my face is as full of wrinkles as the furbelow of a petticoat, and my back arched like a monk's of La Trappe. I give you notice of all this, that, if we should meet again in skin and bone, you may not be shocked at my figure. Nothing belonging to me remains onaltered, except my heart, which, as long as I breathe, will retain its sentiments of affection and tender friendship for my good Mama. Adieu.'
ART. XI. Objervations sur le Commerce de la Mer Noire, &c. i.e. Observations
on the Commerce of the Black Sea, and the adjacent Countries. Tuwhich are added, Remarks on the Trade of Candia and Smyrna. i zino. Amiterdam. 1787, THEcommerce of the Euxine was formerly engrossed by
I the Turks, wno would not suffer the veflels of any European power to navigate this fea; but fince the year 1;83, the Rubans anú Imperialitts have enjoved this privilege, and the French and Dutch Ambadiadors at the Poite, have also en
deavoured to obtain it. These circumstances have induced the anonymous Author of this work to publish his observations, which, he says, were made during his residence in those countries from the year 1759 to 1762. From the preface he appears to be a fugitive from France, residing in Amsterdam. He accuses Louis Antoine Duvalz, a French adventurer, of having stolen a copy of thele observations; and complains that another work of his, of what kind we know not, was surreptitiously carried off to Paris, and being there published, was ascribed to a certain well-known magistrate, whose name however he does not mention. If all this be true, he has been hardly used; but, as he has not thought fit to acquaint the Public with his name, we know not what credit to give to his assertions. The Observations confilt of a short commercial description of the Crimea, and a very minute account of the articles of trade there, in various parts of Turkey, and in the Levant; together with a project for eltablishing a commercial company at Constantinople, and directions concerning the manner of carrying on business in those countries.
ART. XII. Eerste Vervolg der Proefneemingen gedaan met Teylers EleEtrizeer Ma
chine. i. e. Continuation of Experiments performed with the Electrical Machine in Teyler's Museum in Haarlem. By Mar. TINUS VAN MARUM, M. D. Librarian and Director of this Inftitution, Corresponding Member of the Royal Academy of Sciences at Paris, and Member of the Philosophical Societies of Haarlem, Rotterdam, Vlifling, and Utrecht. 4to. Haarlem. 1785. T HIS publication has been unavoidably delayed on account
of the coloured plates, which were necessary to give an adequate idea of some of the phenomena. These plates were executed by M. Sepp, of Amsterdam, an artist, whose accuracy and excellence, in this particular branch, Dr. Van Marum hopes will compensate for the delay occasioned by employing him.
The battery, with which the former experiments were made (see Appendix to our lxxiii. volume), consisted of 135 square feet of coated glass; but the Doctor, thinking that the machine was capable of charging a larger surface, had added to it yo jars, each of the same size with the former; so that his grand battery is now a square of is jars every way, and contains 225 square feet of coated glass. To ascertain the degree of the charge, he uses the Electrometer invented by M. Brook, which is fixed in the center of the battery, at the height of four feet above the knobs of the jars.
His first object was to try whether this battery could be fully charged by the machine, and whether its increase of power
were proportional to the augmentation of its surface. In these respects, his expectations were fully answered. The former battery discharged itself over the uncoated part of the jars, after 96 revolutions; and the present did the same after 160 turns of the machine. With the former battery, the Doctor had split a cylinder of box, three inches in diameter, and three inches in length, the section of which, through its axis, contained nine Square inches. With the 225 jars, he split a fimilar cylinder, four inches in diameter, and four inches in height, the section of which was fixteen square inches. He found that to split a square inch of this wood in the faine direction, required a force equal to 615 pounds, and hence calculates that the power of this ex. plofion was not less than 9840 pounds.
The apparent resemblance between the effects of electricity, and of fire, especially in melting metals, has led many to sup, pore that they act on bodies in a similar manner. In order to examine whether this supposition be juft, Dr. Van Marum caused wires of different metals to be drawn through the same hole, of one thirty-eighth part of an inch in diameter, and ob. served how many inches of each could be melted by the explofion of his battery ; taking care, in all these experiments, to charge it to the same degree, as ascertained by his electrometer. The resulis were as follow : ,
Of lead he melted 120 inches,
31 Of filver, copper and brass, not quite a quarter of an inch. Thele several lengths of wire, of the same diameter, melied by equal explosions, indicate, according to our author, the degree in which each metal is fusible by the electrical discharge ; and, if there be compared with the fufibility of the same metais by fire, a very considerable difference will be observed. According to the experiments of the academicians of Dijon, 10 melt tin required a heat of 172 degrees of Reaumur's cher: mometer. Lead
- 230 Silver
- 4.30 Gold
• 563 Copper - - 630
Iron - - 696 Thus tin and lead appear to be equally fusible by electricity, but not by fire: and iron, which, by fire, is less fusible than gold, is much more so by the electrical explosion. From these and fome other experiments of the same kind, Dr. Van Marum concludes that, in meling metals, the electrical Auid acts upon them in a manner very different from the action of fire, and
that the supposed analogy between these two powerful agents cannot be proved, either from the fusion of metals, or the ignition of combustible substances.
By these experiments on the fusibility of metals, Dr. Van Marum was induced to make trial of the comparative efficacy of lead, iron, brass, and copper, as conductors to preserve buildings from lightning. In this respect, he found that a leaden conductor ought to be four times the size of one of iron, in order to be equal in point of safety. He has also fully proved the superiority of rods to chains, and of copper to iron, for this important use.
When iron wire is melted by the explosion of the battery, the red-hot globules are thrown to a very considerable distance, sometimes to that of thirty feet: this che Doctor juftly ascribes to the lateral force exerted by the electrical fluid. It is however remarkable that, the thicker the wire is, which is melted, the further are the globules dispersed; but this is accounted for, by observing, that the globules, formed by the fusion of thinner wires, being smaller, are less able to overcome the resistance of the air, and are therefore sooner stopped in their motion.
Two pieces of iron wire being tied together, the fusion extended no further, than from the end connected with the inside coating of the jars, to the knot; though wire of the same length and thickness, when in one continued piece, had been entirely melted by an equal explosion.
When a wire was too long to be melted by the discharge of the battery, it was sometimes broken into several pieces, the extremities of which bore evident marks of fusion ; and the effect of electricity, in fhortening wire, was very sensible in an experiment made with 18 inches of iron wire, j's of an inch in diameter, which, by one discharge, loft a quarter of an inch of its length. An explofion of this battery through very small wires, of nearly the greatest length that could be melted by it, did not entirely discharge the jars. On tranímitting the charge through 50 feet of iron wire, of zio of an inch diameter, the Doctor found that the residuum was sufficient to melt iwo feet of the same wire ; but this residuum was much less, when the wire was of too great a length to be melted by the first discharge. After an explosion of the battery through 180 feet of iron wire, of equal diameter with the former, the residuum was discharged through 12 inches of the same wire, which it did not melt, but only blued.
Í wenty-four inches of leaden wire, j's of an inch in diameter, were entirely calcined by an explosion of this battery; the greater part of the lead role in a thick smoke, the remainder was struck down upon a paper laid beneath it, where it formed a Atain, which resembled the painting of a very dark cloud. When Rr4