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pened to the Harriot packet is no more than what often happens to a ship at sea, or to a church, house, or other edifice on land, when the lightning has entered into it, and cannot procure an easy passage out of it. The attempting to procure this easy passage, and thereby avert the mischiefs attending the want of it, is the more particular subject of this communication.

A few years ago the nature of thunder and lightning, which are both to be considered as different appearances of the same meteor, was very little understood. Our predecessors in all ages regarded it as an instrument of Divine vengeance. They stood too much in awe of it to consider it closely; and though the Greeks and Romans* were in possession of some observations which might have led them to a more intimate knowledge of it, they were not apprized that what they saw had any relation therewith. It was not, till by experiments and observations on the nature and properties of electricity, and comparing them. with the phenomena of thunder and lightning, we were informed that electricity and thunder arose from the same cause; or to speak nearer the truth, were different modifications of the same meteor; that they varied in nothing essential, and only differed in being in degree greater or less.

The same means, which taught us the management of one, give us great reason to believe that many of the mischiefs may, by a proper and well disposed apparatus, be prevented of the other. A quantity of electricity, accumulated to a degree sufficient to destroy a large animal, will innocently discharge itself through the smallest wire. And Mr. de Romas in France has found that one of his kites, when flown with a cord composed of hemp and wire, will silently and without any report bring down the matter of thunder from a cloud; though when the apparatus has been altered, and an easy passage has been denied to it, the streams of fire have been seen an inch thick, and 10 feet long, and the report has been equal to that of a pistol. It was owing to this easy passage of lightning being interrupted, that occasioned the death of professor Richmann at Petersburg by his own apparatus.

There is great reason to think, that the mischiefs arising from thunder and lightning happen always near the place where the explosion is made; as those persons who have been present when great mischiefs have been done, universally agree, that when these accidents have happened, the report of the thunder has instantly succeeded the flash of the lightning. As the progress of light is nearly instantaneous, and that of sound somewhat more than 1100 feet in a second of time, the thunder and lightning happening in the same instant proves the explosion to have been very near. We are therefore to guard against the thunder clouds which are near us. The mast of every ship, which is beset on its tops

* See Plutarch in the life of Lysander, Pliny, Seneca, Cæsar, Livy, &c.-Orig.

with those bright lights, which our mariners call comazants, and are the feu St. Elme of the French, and were the Castor and Pollux of the ancients, is within the sphere of action of a thunder cloud. Anciently, when these were seen, they were only considered as the attendants of a storm, and no consequence was drawn from them; but now, (since Dr. Franklin's admirable discovery of conducting lightning from the clouds, we know them to be no other than a modification of the same meteor, which constitutes thunder and lightning) they demonstrate that danger is near, and therefore we should do our utmost to prevent its effects. This in Dr. W.'s opinion would be done, if a wire of iron or any other metal were connected with the spindles and iron work at the tops of masts of ships, and conducted down the sides of the masts, and from thence in any convenient direction so disposed as always to touch the sea-water. By these means, the accumulation of the matter of thunder and lightning will be prevented, to a considerable distance from the ship, by its being discharged silently by the wire, which will not be done by the masts; as these from their height, figure, and constituent parts, without an apparatus of this kind, tend to direct and conduct the lightning into the ship. But for a further explanation on this head, Dr. W. refers to p. 215, vol. 48 of the Phil. Trans., where he had considered this matter more at large.

The applying wire to the masts of ships will be neither difficult nor expensive; as a brass wire of the thickness of a large goose quill, will in most cases be large enough to answer this purpose. He prefers brass wire to iron, as less liable to rust; and any metal corroded by rust, to the centre, ceases to be of any use in directing the lightning, in the degree hoped for and expected by this apparatus. He declines entering into a minute detail of the rationale of this process; but from analogy only he mentions that the same quantity of gunpowder, which confined in a close place, will throw down a tower, or rend a rock, will, when fired loose in the open air, be almost inoffensive.

Thunder storms are very frequent and severe in Pennsylvania, and great mischiefs often happen from them; Dr. W. was informed by Dr. Franklin, that since an apparatus of the kind above mentioned, placed at the tops of the houses, has been generally used at Philadelphia, not a single instance of mischief from lightning had happened in that city. He informs further, that at Philadelphia in a thunder storm, the lightning was seen to strike the ridge of a house, on which an apparatus of this sort was erected. The lightning, like a ball of fire, ran from the ridge of the house to the apparatus, and in running down, it melted the conducting wire, without doing any damage to the house. This shows the expediency of applying either large wires or small rods, in which the melting will most probably be prevented; notwithstanding it has been repeatedly found, that

though the wire has been melted, it has never failed of first answering the purpose of a conductor, and preventing the mischiefs threatened by the lightning. Though the mischiefs arising from lightning are not very frequent in Great Britain, yet at times they are severe enough to be very alarming. The damage occasioned by a thunder storm in July 1759 in London, and in various other places at no great distance from it, are very fresh in our memories. Dr. W. submits it therefore how far it would be attention misapplied to think of an apparatus of this sort in his Majesty's powder magazine, erecting at Purfleet. The expence would be trifling; and every argument which is produced of their expediency in preventing mischiefs arising from lightning on board of ships, will have more force in this instance; where frequently an immense quantity of gunpowder must be collected within a comparatively very small space.

CII. On the Case of the late Rev. James Bradley, D.D. Astronomer Royal. By Daniel Lysons, M.D. p. 635.

Dr. Bradley had laboured under a great oppression of spirits for a long time; and for several years before his death frequently complained of a pain in his back, sometimes attended with difficulty in the discharge of his urine, which he apprehended to proceed from the gravel. On Wednesday June 30, 1762, he rode out for the air, and on coming home complained of pain in his back, and made a large quantity of water. At 5 o'clock the next morning he found himself labouring under a total suppression of urine, from which time he never voided any without the assistance of the catheter. With its assistance however about a quart was drawn off every 12 hours, excepting one intermission; when on account of the difficulty of introducing the catheter, none was drawn off from Friday morning July the 9th, till 8 o'clock on the Saturday evening. But both before and after that time the urine was regularly drawn off every morning and evening to the time of his death, on the 13th of July.

During his illness he often complained of pains in the abdomen. And his head was frequently disordered, especially when a stool was coming away; but after that had passed off, he was always more cool and reasonable. It was the opinion of Dr. Jones, who attended him constantly in the country, as well as of Dr. Lewis, and Dr. Lysons who visited him occasionally from Oxford, that his pains were inflammatory, though not violently so. But where the inflammation was exactly seated, they could not precisely determine; as it seemed often to shift its situation, and the patient was himself incapable of giving them the necessary description, his weak state obliging him to signify his meaning more by signs than words, and those not always intelligible. As nothing positive could therefore be said with regard to the seat of the disorder, the friends of the deceased desired that his body might be opened; and Dr. Jones and Dr. L. being present at the operation,

the latter physician minuted down such appearances as presented themselves to their view, and collected the following observations.

The small intestines, the exterior coat of the stomach, and concave part of the left lobe of the liver, were all considerably inflamed. The gall bladder was very large and full of bile. The fat inclosed in the cellular membrane, surrounding the right kidney, was considerably wasted, and very much indurated; and appeared to adhere more firmly than usual to the external surface of the kidney. On removing this kidney with its fat, all the parts adjacent appeared much inflamed. The whole kidney was soft, and contained matter so disseminated through its whole substance, that it issued out on pressure from every part; in the same manner as an absorbed fluid does from the pores of a sponge. No stone or gravel were found in the pelvis, or any other part of the right kidney. The left kidney was nearly of the same pulpy substance with the right; equally contained matter, though not so large a quantity, and was equally free from stone and gravel. The vena cava, and the emulgent vein of the left kidney, were remarkably large. The aorta was ossified near its bifurcation into the crural arteries. - Two unnatural tumours grew on the left and lower side of the pelvis internally, near the junction of the os pubis with the ischium. They were contiguous to each other; in circumference severally something less than a walnut: and both taken together were 3 inches or more in length. When cut through, they had the appearance of glands, and one of them contained matter, disseminated through its substance in the same manner as the kidneys. On examining the bladder, the prostate gland was found enlarged and indurated, and the internal coat of the bladder itself inflamed. But neither the bladder, nor the ureters, contained any stone or gravel. No morbid appearance was observed in the liver, lungs, or any other of the parts, besides those above mentioned.

From the above observations it appears that this case was a general inflammation in most of the contents of the abdomen, and that the suppression of urine was probably a symptom in consequence of the swelling and induration of the prostate gland which thereby closing the neck of the bladder, made the use of the catheter necessary. That the constitution was become extremely purulent. But as these collections of matter do not appear to have destroyed any of the vital functions, so it seems reasonable to believe that the immediate cause of his death was a general inflammation, and consequential sphacelus, in some of the abdominal contents.

Instances of abscesses formed in the kidneys, from the lodgment of calculi, are not unfrequent; but then the papillæ of the kidneys being irritated and inflamed by the stone, and in consequence the secretory tubes dissolved into matter, the secretion is thereby destroyed, and a suppression of urine always takes place in regard to that kidney. Two cases are indeed mentioned, the one by Eustachius

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the other in the Miscellanea Curiosa, where the kidneys in one of the subjects, are said to have been found putrid, in the other semiputrid, and no calculus in either. Such cases as these are very uncommon, and bear some resemblance to the case before us; in which it is very remarkable, that though matter was intimately distributed through every part of the kidneys, yet the tubuli forming the urinary organs of secretion remained sound, and properly qualified to perform their functions even till death; as appeared by the urine being drawn off every 12 hours, till near the time of the patient's decease, and the bladder being found distended with urine on opening the body. Whereas in the case recorded in the Miscellanea Curiosa, after a total suppression of urine, the bladder was found small and contracted, no urine having been excreted from the kidneys into it. That the matter did not in the present case insinuate into, or in any manner disturb the urinary secretion is evident; since no pus was ever observed in the urine either before or after the introduction of the catheter. How this extraordinary case comes to be so particularly circumstanced seems worthy of considera


CIII. Experiments to Prove that Water is not Incompressible. By John Canton, M. A., F. R. S. p. 640. Having procured a small glass tube of about 2 feet in length, with a ball at one end of it, of an inch and a quarter in diameter; Mr. C. filled the ball and part of the tube with mercury; and keeping it with a Fahrenheit's thermometer in water which was frequently stirred, it was brought exactly to the heat of 50 degrees; and the place where the mercury stood in the tube, which was about 6 inches above the ball, was carefully marked. He then raised the mercury by heat to the top of the tube, and sealed the tube hermetically; and when the mercury was brought to the same degree of heat as before, it stood in the tube of an inch higher than the mark. The same ball and part of the tube being filled with water exhausted of air, instead of the mercury; and the place where the water stood in the tube when it came to rest in the heat of 50 degrees, being marked, which was about 6 inches above the ball; the water was then raised by heat till it filled the tube; which being sealed again, and the water brought to the heat of 50 degrees as before, it stood in the tube of an inch above the mark.

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Now the weight of the atmosphere, or about 73 pounds avoirdupois, pressing on the outside of the ball and not on the inside, will squeeze it into less comAnd by this compression of the ball, the mercury and the water will be pass.*

• See an account of experiments made with glass balls by Mr. Hooke, (afterwards Dr. Hooke,) in Doctor Birch's History of the Royal Society, vol. 1, p. 127.

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