and mostly carried overboard. Here also the mainmast was made of fir, and the part which was split and shivered to pieces, was the part usually coated with turpentine, mixed as before said with tallow or oil: and the main topmast, which was made of a wood of the country called teak, and is of a texture like oak, but stronger, was untouched, notwithstanding it lay parallel and touched the mast for the whole length of the part carried away.

[Id. 1764.

15. Effects of Lightning on a Hulk at Plymouth,

By John Huxham, M. D.

SUNDAY, December 15, 1754, twenty-five minutes after one P. M. a vast body of lightning fell on the great hulk at Plymouth. dock, which serves to boist in and fix the masts of the men of war. It burst out about a mile or two to the westward of the hulk, and rushed with incredible velocity towards it. The piece of the Derrick cut out was at least eighteen inches diameter, and about fifteen or sixteen feet long: this particular piece was in three or four places begirt with iron hoops, about two inches broad, and half an inch thick, which were completely cut in two by the lightning, as if done by the nicest hand and instrument. The lightning was immediately succeeded by a dreadful peal of thunder, and that by the most violent shower of hail, which fell only in and about this town, for a mile or two; there was very little of it at the dock, though only two miles distant. The hail stones were as large as small nutmegs, all very nearly of the same size and shape. They measured, immediately after they fell, near two inches [Id. 1755.

round.

16. Thunder-clap, with an extraordinary fire-ball, bursting

at sea.

By Mr. Chalmers.

Nov. 4, 1749, in the latitude of 42° 48′, longitude 9° 3′, the Lizard then bore N. 41° 5' about the distance of 569 miles, as Mr. C. was taking an observation on the quarter.deck, about ten mi. nutes before 12 o'clock, one of the quarter.masters desired he

would look to windward, which he did, and observed a large ball of blue fire rolling on the surface of the water, at about three miles distance from them. It came down upon them so fast, that before they could raise the main tack, they observed the ball to rise almost perpendicular, and not above forty or fifty yards from the main chains: it went off with an explosion as if hundreds of cannon had been fired at once; and left so great a smell of brim. stone, that the ship seemed to be nothing but sulphur. After the noise was over, which did not last longer than half a second, they found the main-topmast shattered into above a hundred pieces, and the mainmast rent quite down to the heel. There were some of the spikes, that nailed the fish of the mainmast, drawn with such force out of the mast, that they stuck in the main deck so fast, that the carpenter was obliged to take an iron crow to get them out: five men were knocked down, and one of them greatly burnt, by the explosion. They thought that when the ball, which appeared to be of the size of a large millstone, rose, it took the middle of the main-topmast, as the head of the mast above the hounds was not splintered. The ball came down from the N. E. and went to the S. W. [Id. 1750.

17. Singular effect of thunder and lightning on sea-compasses.

In a letter from Dublin.

MR. Haward, a very creditable person, tells me, that being once master of a ship in a voyage to Barbadoes, in company with another commanded by one Grafton, of New-England, in the latitude of Bermudas, they were suddenly alarmed with a terrible clap of thunder, which broke Mr. Grafton's foremast, tore his sails, and damaged his rigging. But that after the noise and con. fusion were past, Mr. Haward, to whom the thunder had been more favourable, was however no less surprised to see his com. panion's ship steer directly homeward again. At first he thought that they had mistaken their course, and that they would soon perceive their error; but seeing them persist in it, and being by this time almost out of call, he tacked and stood after them; and as soon as he got near enough to be well understood, asked where they were going; but by their answer, which imported that they had no other design than the prosecution of their former intended

toyage, and by the sequel of their discourse, it at last appeared that Mr. Grafton did indeed steer by the right point of his com. pass, but that the card was turned round, the north and south points having changed positions; and though with his finger he brought the fleur-de-lys to point directly north, it would immedi ately, as soon as at liberty, return to this new unusual posture; and, on examination, he found every compass in the ship altered in the same manner; which strange and sudden accident he could impute to nothing else but the operation of the lightning or thunder just mentioned. He adds, that those compasses never, to his knowledge, recovered their right positions again,

[Id. 1676.

18. Another instance of the above, with greater damage to the Vessel.

By Captain John Waddle.

ON January 9, 1748-9, the new ship Dover, bound from New York to London, being then in latitude 47° 30′ north, and longitude 22° 15′ west, from London, met with a very hard storm of wind, attended with thunder and lightning, as usual, most part of the evening, and sundry very large comazants, as they are called, overhead, some of which settled on the spindles of the top-mast heads, which burnt like very large torches; and at 9 p. m. a sin. gle loud clap of thunder with lightning struck the ship in a violent manner, which disabled Captain W. and great part of the ship's company in the eyes and limbs; it struck the mainmast about up almost half through, and stove the upper deck, one carling, and quick-work; part of which lightning got in between decks, started off the bulk-head, drove down all the cabins on one side of the steerage, stove the lower deck, and one of the lower deck main lodging-knees. Another part of it went through the starboard side, without any hurt to the ceiling, or inside plank; and started off from the timbers four outside planks, being the wale upwards; one of which planks, being the second from the wale, was broke quite asunder, and let in: in about ten or fifteen minutes time nine feet water in the ship.

It also took the virtue of the loadstone from all the compasses, being four in number, all in good order before, one in a brass and

three in wooden boxes. The hanging compass in the cabin was not quite so much disabled as the rest; they were at first very near reversed, the north to the south; and after a little while ram. bled about so as to be of no service. The storm lasted five days; they lost the mainmast and mizenmast, and almost all the sails; and arrived at Cowes the 21ts of January in a very shattered condition. [Phil. Trans. 1749.

19. Examination of the preceding Mariner's Compass; and the Explanation of the Cause of its reversed polarity.

By Gowin Kuight, M.B. F.R.S.

On examining the compass struck with lightning, it appeared that the outward case was joined together with pieces of iron wire, sixteen of which were found in the sides of the box, and ten in the bottom. Mr. K. applied a small needle to each of these wires, and immediately perceived that the lightning had made them strongly magnetical; particularly those that joined the sides. All the heads of the wires on one side of the box attracted the north point of the needle and repelled the south; while all the heads on the other side attracted the south and repelled the north; the wires at the bottom attracted the south and repelled the north; but it is not certain whether this polarity was any wise owing to the lightning; since it might be acquired by their continuing long in an erect position.

On examining the card, he found the needle was vigorous enough in performing its vibrations, but that its polarity was inverted; the north point turning contrary to the south. He then tried to take out the card, to examine the state and structure of the needle: but the junctures, every where were well secured with putty, be come so hard, that he was obliged to use some violence, and at last broke the glass. The needle consisted of two pieces of steel wire, each bent in the middle, so as to make an obtuse angle; and the ends of these wires applied together, forming an acute one, the whole appearing in the shape of a lozenge; in the centre of which was placed a brass cap on which the card turned. And so far was it from being made with any tolerable degree of exactness, that there was not the least care taken either to bend the wires in the middle, or to fix the cap exactly in the centre of the lozenge.

The pin on which it turned, was made of a slip of plate brass, sharpened to a point.

Besides the particulars already communicated to the Society, the captain informed him, that he was obliged to sail above 300 leagues, after this accident happened, without a compass, till he arrived at Cowes in the Isle of Wight; where being provided with one, he placed it in the binacle, but was much surprised to find that it varied from the direction it stood at when out of the binacle nearly two points. He removed the binacle to different parts of the deck, but found that it always made the needle to vary after the same manner when placed in it. He repeated the same experiment lately in the river, with the like success; only that he observed, that the variation of the needle, when placed in the binacle, was rather less than at first. It was natural to inquire if there was any iron about the binacle; but the Captain said he had given strict charge to the maker not to put so much as a single nail in it; and that he firmly believed that there was not the least bit of iron about it.

Being willing to be satisfied of the truth of a circumstance so very extraordinary, the captain was desired to send the binacle to a house in the city; where, in company with the Captain, Mr. Ellicot, and another gentleman, Mr. K. tried it with a large compass touched by his bars; but finding no sensible variation, they at that time desisted, thinking the fact quite improbable; but having discovered the effect which the lightning had produced on the wires which fastened the sides of the compass box, he was induced to ex. amine the binacle a second time; which he did with a small compass, and with great care, in every part; and at last, about the middle of the binacle, he found it to vary very sensibly, but could not discover any nails or iron thereabouts; till turning it up to examine the bottom, he there found three or four large nails, or rather spikes, driven through it to fasten the upright partitions in the middle of the binacle.

It would not be difficult to explain why any needles, under such circumstances, should be rendered useless by lightning, though the needles themselves had remained unhurt. So many iron wires made strongly magnetical would doubtless have effected it; and three or four large nails in the binacle, if made magnetical, would alone have been sufficient to have done it. But it has always been noticed that the polarity of the needle was inverted by this acci.