1. All hurricanes come either on the day of the full, change, or quarters of the moon. 2. If it be to happen on the full moon, observe these signs during the change: the skies will be turbulent, the sun redder than usual, a great calm, and the hills clear of clouds or fogs over them, which in the high lands are seldom so; likewise in hollows, or concaves of the earth, or wells, there will be a great noise, as of a storm, and at night the stars will look very large with burs about them, and the north-west sky very black and foul, the sea smelling stronger than at other times: and sometimes for an hour or two of that day the wind blows very hard westerly out of its usual course. On the full of the moon you have the same signs, with a great bur about the moon, and frequently about the sun. The same signs must be observed on the quarter days of the moon, in July, August, and September, the months when the hurricanes are most prevalent. The earliest I ever heard of was the 25th of July, and the latest the 8th of September; but the usual month is August.

The causes of these hurricanes, according to experimental observations of my time, are these:

1. It is known to men of experience, that to the southward of the tropics there is constantly a trade-wind, or easterly wind, which goes from the north to the south-east all the year round; except were there are reversions of breezes, and inlets near the land; so that when this hurricane, or rather whirlwind, comes in opposition to the constant trade-wind, then it pours down with such violence as exceeds any storms of wind. In the hurricane at Nevis, I saw the high mountain that was covered with trees left in most places bare.

2. It is remarked by all men, that have been in those parts where the sun comes to the zenith, that at his approach towards it, there is always fair weather; but at his return southwards, it occasions, off the north parts of the equinoctial, generally much rain and storms, as tornadoes, and the like which makes the wind in the tornado come on several points. But before it comes, it calms the constant easterly winds; and when they are past, the easterly wind gathers force again, and then the weather clears up fair.

3. The wind being generally between the tropics and the equator easterly, unless at such times as before mentioned; meeting with the opposition of these hurricanes, which come in a contrary course to that trade-wind, causes this violent whirlwind, on the sun's leaving the zenith of Barbadoes, and these adjacent islands; by which the easterly wind loses

much of its strength; and then the west wind, which is kept back by the power of the sun, with the greater violence and force pours down on those parts where it gets vent. And it

is usual in sailing from Barbadoes, or those islands to the north, for a westerly wind, when we begin to lose our easterly wind, to have it calm, as it is before hurricanes: and then the wind springing up, till it comes to be well settled, causes the weather to be various; but after the settled westerly wind comes fresh, they have been constantly without those shufflings from point to point.

Here it is to be observed, that all hurricanes begin from the north to the westward, and on those points that the easterly wind blows most violently, the hurricane blows most fiercely against it; for from the N. N. E. to the E. S. E. the easterly blows, freshest; so does the W. N. W. to the S. S. W. in the hurricane blow most violent; and when it comes back to the S. E., which is the common course of the trade-wind, then it ceases of its violence, and so breaks up. Thus I take the cause of hurricanes to be the sun's leaving the zenith of those parts towards the south; and, secondly, the reverse or rebounding back of the wind, which is occasioned by the calming of the trade-wind.

Some Experiments and Observations concerning Sounds. By Mr. WALKER. - [1698.]

INTENDING to try the swiftness of sounds, I provided a pendulum, which had two vibrations in 1" of time: this I carefully adjusted at a watchmaker's: it was a piece of small virginal wire, with a pistol bullet at its end; the length was 9 inches to the middle of the bullet: I first made it about of an inch longer, viz. one fourth of the length of a pendulum that vibrates seconds, but found it too slow, which I expected from the air's resistance.

ΤΟ

Here follow the numbers, in English feet, which sound moved in one second of time at several trials:

Mersenne mentions an experiment, in which he motion of sound to be 1174 feet in a second.

found the And the

Academy del Cimento caused six harquebusses and six chambers to be fired, one after another, at the distance of 5739 English feet, and from the flash to the arrival of each report was 5"; and repeating the experiment at the midway, the motion was exactly in half the time, which gives 1148 feet per second. Mr. Boyle also mentions that he has more than once diligently observed, that the motion of sound passes above 400 yards, or 1200 feet in 1".

Mersenne and the Academy del Cimento conclude, that sounds are all of the same quickness, whether they be great or small, and whatever temper the air is of, though Mersenne was once of another mind: but Kircher, from several experiments, infers, that loud sounds move quicker than small ones. Dr. Plot says, an echo returned the sound of a pistol much quicker than that of the voice; and that it repeated more syllables in the night than in the day; whence it follows that the sound moved slower in the night than in the day. Kircher says, that an echo, which in the night repeated 14 syllables, repeated only seven in the day. Because there seems to be so great affinity between the undulations of water and the propagation of sound, the Academy del Cimento tried some experiments about the first; and they tell us, that the larger the stone is, which is thrown into the water, and the greater the force, by so much is the undulation swifter.

On the Generation of Fleas. By Sig. D. CESTOne.

FLEAS bring forth eggs, or a sort of nits, from which are hatched worms; these make bags like silk-worms, and from these bags come fleas. They deposit their eggs on dogs, cats, men, and other animals infested with them, or in places where they sleep, which being round and smooth, slip commonly down to the ground, or fix themselves in the folds or other inequalities of the coverlets and clothes. From these are brought forth white worms, of a shining pearl colour, which feed on the branlike substance which sticks in the combs when puppies are combed to take out the fleas; or on a certain downy substance that is found in the folds of linen, or other similar things.

In a fortnight's time they are very lively and active: if they have any fear, or be touched, they suddenly roll themselves up, and become as it were a ball. A little after they creep as silk-worms do that have no legs, with a brisk and swift motion. When they are come to their usual size, they hide themselves as much as they can, and bringing out of

H

their mouths the silk, they make round themselves a small bag, white within as paper, but without always dirty and fouled with dust. In two weeks more, in the summer-time, the flea is perfectly formed; then it soon leaves its exuvia in its bag, as silk-worms and all caterpillars do; which leave in the same their exuvia. The flea, so long as it is enclosed

On Sable Mice, which have lately come in Troops into Lapland, about Thorne, and other Places adjacent to the Mountains. By Sir PAUL RYCAUT, F.R.S.-[1699.] In the year 1697 these sable mice were first observed, and are nearly as large as a small squirrel: their skin streaked, and spotted black and light brown; they have two very pointed teeth above, and two below; their feet like those of squirrels: they are so fierce and angry, that if a stick be held out at them they will bite it, and hold it so fast, that they may be swung about in the air: they are fat and thick, and without any tail.

In their march they keep a direct line, generally from north-east to south-west, and are innumerable, thousands in each troop, which for the most part is of a square figure: they march by night and in the twilight, and lie still by day. The distance of the lines they go in is of some ells, all parallel to each other, so that the places they have gone over look

2

like the furrows in a ploughed field. If they meet any thing that might stop them, they avoid it not, though it were a fire, a deep well, a torrent, lakes, or morass, but without any hesitation venture through, and by that means many thousands of them are destroyed, and found dead in waters, and otherwise.

If they be met swimming over lakes, and attacked with oars or boat-hooks, they neither retreat, nor offer to run up the oars, &c. but hold on their course, and if forced out of it they presently return to it again. When they are met in woods or fields, and stopped, they set themselves on their hinder feet like a dog, and make a kind of barking or squeaking noise, leaping up as high as a man's knee, defending their line as long as they can; and if at last they be forced out of it, they creep into holes, and set up a cry sounding like biabb, biabb.

They never come into any house, nor meddle with any thing that is food for man: if a house happen to be in their way, there they stop till they die; but through a stack of hay or corn they will eat their way when they march through a meadow they injure it much by eating the roots of grass; but if they encamp there by day they quite spoil it, and make it look as if it were burnt, or strewed with ashes. The roots of grass, with rotten wood, and the insects in it, are their chief if not only food. These creatures are very fruitful, and bring forth eight or nine at a time; yet this does not hinder their march; for some of them have been observed to carry one young one in their mouth, and another on their back.

It is reported that some poor Laplanders, wanting other food, have killed and ate several of these creatures, and found their flesh like that of squirrels: dogs and cats, when they kill them, eat only the heads, and birds of prey only the heart during the winter they lie under the snow, and have their breathing holes upon the top of it, as hares and other creatures. The common people are very glad of these guests, as they foretell plenty of game, as fowl, squirrels, lo-cats, foxes, &c.

These mice are the same with those called mures Norwegici, Norway mice, described by Olaus Wormius in his museum, now Lemming's.

On the Cures performed by Mr. Greatrix, the Stroker. By Mr. THORESBY. -[1699.]

THE first instance I shall mention of his cures was my