to end over the Causeway, and he thinks become shorter and shorter as one goes from it, lying between two binds of stone like seams of coal, and like those little pillars found in Derbyshire. These binds probably meet together all round, and inclose this extraordinary work of nature; and if so, the pillars must be very short towards the extremities.

When on the Causeway, he saw in the cliff, to the southeast, what they call the Organs, about a quarter of a mile off, and a third part of the way up the cliff. They appeared small, and somewhat like black stalactites: they were not commonly known to be such pillars as the others; but they are so, and belong to the lower stratum. When with great difficulty he climbed up the steep hill to them, he found they were hexagonal, and larger pillars than most of the others, being about two feet in diameter; and he measured five sides of one of them, which were of 13, 15, 12, 21, and 16 inches respectively. The joints he could come at were about nine inches thick, and each pillar consisted of between 40 or 50 of them these joints are almost flat and plain, the convexities on their upper faces being so small as to be scarcely discernible. He enquired whether any of these pillars were found in the quarries within land, and the people there told him they were not; but he has since been assured by others, that there are some found two or three miles from the shore.

On the Everlasting Fire in Persia. By Dr. JAMES MOUNSEY.

As the natural history of Persia is but little known, and the authors of the Universal History have given no true account of the everlasting sacred fire which the Gauers worship, Dr. M. gives the following description of it:

This perpetual fire rises out of the ground in the peninsula of Abscheron, about 20 miles from Baku, and three miles from the Caspian shore. The ground is very rocky, but has a shallow covering of earth over it. If a little of the surface be scraped off, and fire be applied to the hollow, it catches immediately, and burns without intermission, and almost without consumption; nor is ever extinguished, unless some cold earth be thrown over it, by which it is easily put out.

There is a spot of ground, about two English miles broad, which has this very wonderful property; and here is a caravansary, round which are many places where the earth continually burns; but the most remarkable is a hole about four feet deep, and 14 feet in diameter. In this caravansary live 12 Indian priests, and other devotees, who worship

the fire, which, according to their traditions, has burnt many thousand years. It is a very old vaulted building, and in its walls are a great many chinks, to which, if a candle be applied, the fire catches instantaneously, and runs instantly wherever the chinks communicate; but it may be easily extinguished. They have hollow places in the house fitted to their pots, which they boil without any other fuel; and instead of candles they stick reeds into the ground; from the tops of which, on applying fire to them, a white flame immediately comes forth, and continues to burn without consuming the reeds, till they think proper to extinguish it, by putting little covers over them for that purpose.

About an English mile and a half from this place there are wells of white naphtha, which is exceedingly inflammable; and though the flame of naphtha affords both smoke and smell, it is highly probable the perpetual fire just described is owing to naphtha, but so purified, in filtering through the stone, that it becomes divested of all such particles as produce smoke or smell. The stone and earth are grey in colour, and saltish to the taste; and indeed much salt is found on this peninsula of Abscheron. There is also a salt lake, near the side of which the white naphtha flows by five different springs. This naphtha is made use of only for medicinal purposes. It is yellowish from the spring, but when distilled resembles spirits of wine. They give it internally for gonorrhoeas, disorders of the breast, and for the stone, and they apply it externally in gouty cases, and contractions of the sinews. Black naphtha is produced eight or nine miles from the perpetual fire: it is thick, and being distilled becomes not clear, but yellow. The best, and greatest plenty, is at Balachame, where there are above 50 springs, the greatest producing every day 500 batman, each batman_containing ten Russ pounds, which are somewhat less than English weight.

Of the Locusts, which did vast Damage in Wallachia, Moldavia, and Transilvania, in 1747-8.

THE first swarms entered into Transilvania in August, 1747; these were succeeded by others, which were so surprisingly numerous, that when they reached the Red Tower, they were full four hours in their passage over that place; and they flew so close, that they made a sort of noise in the air, by the beating of their wings against each other. The width of the swarm was some hundreds of fathoms, and its height or density may be easily imagined to be more considerable, inasmuch as they hid the sun, and darkened the sky, even to

that degree, when they flew low, that people could not know one another at the distance of 20 paces. But as they were to fly over a river that runs in the vallies of the Red Tower, and could find neither resting-place nor food; being at length tired with their flight, one part of them lighted on the unripe corn on this side of the Red Tower, such as millet, Turkish wheat, &c.; another part pitched on a low wood: where having miserably wasted the produce of the land, they continued their journey, as if a signal had been actually given for a march. The guards of the Red Tower attempted to stop their irruption into Transilvania by firing at them; and indeed where the balls and shot swept through the swarm, they gave way and divided; but, having filled up their ranks in a moment, they proceeded on their journey.

Wherever those swarms happened to pitch, they spared no sort of vegetable; they ate up the young corn, and the very grass; but nothing was more dismal to behold than the lands in which they were hatched; for they so greedily devoured every green thing there, before they could fly, that they left the ground quite bare.

On the Lacrymæ Batavica, or Glass Drops. By CLAUD. NIC LE CAT, M.D. F.R. S.-[1749.]

THE glass-tear, or drop, commonly called lacryma Batavica, or lacryma Borussica, because it was first made in these countries, is much celebrated among natural philosophers, on account of the singular phenomena which it exhibits, and which have for a long time exercised their sagacity. The make of this drop is as simple as its explanation is difficult. It is the work of the meanest workmen in a glass-house. On the top of an iron rod they take up a small quantity of the matter of glass in fusion: they let it drop into a pail of water: the drop makes that part of the water which it touches to boil with a hissing noise, as red-hot iron does, which it resembles in that instant; and when it does not break in this operation, as it most frequently does, it forms a little pyramidal mass, which is known by the name of a glass-drop.

The drop is of such hardness and resistance, that it bears smart blows of a hammer, without breaking. Yet if you grind the surface of this drop which resisted the hammer, or if you only break the tip of the small end or tail, the whole shatters into powder. This shattering of the drops is attended with a loud report; and the dust or powder, to which it is reduced, is extensively scattered all around. If the drop be

ground with powder of emery, imbibed with oil, it often escapes breaking. If this experiment be made in the air-pump, the drop busts with greater impetuosity, so as sometimes to break the receiver; and its dust is finer than when done in the open air; and if it be made in the dark, the drop in bursting produce a small light. If this drop be annealed in the fire it looses all these singularities; and being reduced to the state of common glass, it easily breaks under the hammer; and does not burst on breaking the small end. The drops that are made by letting them cool in the air produce no other effects than those which have been annealed.

The first natural philosophers who endeavoured to investigate the cause of this phenomena, imagined that they found it in the air. Some of them supposed, that this air was shut up in the drop by the crust which the cold water forms on its surface while it is yet red-hot; and attributed its rupture to the violence with which this air issued through the too narrow passage made for it, in breaking the small end of the drop. Others maintained, on the contrary, that the drop, in this state, contained no air at all, nor any thing but particles of fire, or subtile matter; în short, a mere vacuum as to air; and that the sudden bursting of the drop was occasioned by the impetuous entry of the air into this kind of vacuum.

It is among the glass-workers, and in their art, that the secret of the glass-drop is to be sought; and there it is that he discovered it. Those who have seen glass-houses know, that when a piece fails in the hands of a workman, he throws it aside; and this piece is not long exposed to the air before it breaks in pieces; and when the same workman has succeeded in making a piece, and is willing to preserve it, he takes great care not to let it cool in the air; but carries it hot into another oven of a moderate heat, where he leaves it for a certain time; and this last operation is called annealing the glass.

A natural philosopher who is witness to this managment, ought to enquire into the reasons and necessity of it. How comes it that the glass which cools in the air breaks, and when it has been annealed, it does not break? This is the reason. A bit of melted glass, red-hot and liquid at the same time, is in that state, purely because its particles are divided by fire, or so violently agitated, that these component parts of the glass hardly touch each other.

When this substance is exposed to the air, the coolness of this fluid, which touches the surface of the glass, cools that surface first; that is, brings the particles nearer together,

braces their pores, and thus imprisons the crystals, which stik fill the inside of this substance. While these fired particles find pores enough on the surface to move freely, the glass continues whole; but when the glass grows colder, that is, when the pores of its surface begin to confine these fired particles, then their whole action is exerted against the parts of the glass, which they break into a thousand pieces.

Letter from LEONARD EULER, Prof. Math. at Berlin, and F.R.S. concerning the gradual Approach of the Earth to the Sun.

M. LE MONNIER writes to me, that there is at Leyden an Arabic manuscript of Ibn Jounis, which contains a history of astronomical observations. I am very impatient to see such a work which contains observations that are not so old as those recorded by Ptolemy. For having carefully examined the modern observations of the sun with those of some centuries past, though I have not gone farther back than the 15th century, in which I have found Walther's observations made at Nuremberg, yet I have observed that the motion of the sun, or of the earth, is sensibly accelerated since that time, so that the years are shorter at present than formerly; the reason of which is very natural: for if the earth, in its motion, suffers some little resistance, which cannot be doubted, the effect of this resistance will gradually bring the planets nearer and nearer the sun; and as their orbits thus become less, their periodical times will also be diminished. Thus in time the earth ought to come within the region of Venus, and at last into that of Mercury, where it would necessarily be burnt. Hence it is manifest that the system of the planets cannot last for ever in its present state. It also incontestably follows, that this system must have had a beginning: for whoever denies it must grant that there was a time when the earth was at the distance of Saturn, and even farther, and, consequently, that no living creature could subsist there.

Letter from Mr. Professor EULER concerning the Contraction of the Orbits of the Planets. [1750.]

I AM still thoroughly convinced of the truth of what I advanced, that the orbs of the planets continue to be contracted, and, consequently, their periodical times grow shorter.

The late Dr. Halley had also remarked, that the revolu