which the sea perpetually covers, and have more than 30 feet water above them. But these are sufficient to confirm the ancient tradition of these parts, that St. Michael's mount, now half a mile inclosed with the sea, when the tide is in, stood formerly in a wood. That the wood consisted of oak, very large, hazel and willow trees, is beyond dispute. That there has been a subsidence of the sea-shores hereabouts, is hinted in a former letter; and the different levels and tendencies, observed in the positions of the trees found, afford some material inferences as to the degree and inequalities of such subsidences in general; as the age in which this subsidence happened (near 1000 years since at least) may convince us that when earthquakes happen, it is well for the country that they are attended with subsidences; for then the ground settles, and the inflammable matter, which occasioned the earthquake, has no longer room to spread, unite, and recruit its forces, so as to create frequent and subsequent earthquakes; whereas, where there are earthquakes without proportionable subsidences, there the caverns and ducts under-ground remaining open and unchoaked, the same cause, which occasioned the first, has room to revive and renew its struggles, and to repeat its desolations or terrors, which is most probably the case of Lisbon.

X. Experiments on applying Dr. Hales's Method of Distilling Salt-water to the Steam Engine. By Keane Fitzgerald, Esq. F. R. S. p. 53.

On reading Dr. Hales's account of purifying salt water, by blowing showers of air through, it occurred to Mr. F. that something of the kind might be applied with advantage to the steam or fire-engine, by increasing the quantity of steam, and consequently diminishing the quantity of fuel otherwise necessary. As the strength of steam raised from boiling water is always in a fluctuating state, and has never been found above stronger or weaker than air; he was in doubt whether steam, produced by this method, would be sufficiently strong for the purpose of the steam-engine.

Mr. F. made an experiment first on a small boiler, about 12 inches diameter, made in the shape of those commonly used in steam-engines, with a funnel at the top, of about 1 inch diameter, for the steam to pass through, the aperture of which was covered with a thin plate, fixed at one end with a hinge, and a small leaden weight to slide on the other, in the nature of a steel-yard, to mark the strength or quantity of the steam. A tin pipe made for this purpose, with several small holes towards the end, passed from a small pair of bellows, through the upper part of the boiler, to within about an inch of the bottom. The boiler was half filled with water, which covered the holes in the pipe about 6 inches. From the best observation he was capable of making with this machine, by blowing air through the boiling water, it produced about more steam than was

produced by the same fire without blowing air through. He then applied a machine of this kind to the engine at the York-buildings water-works, the boiler of which is 15 feet diameter. It has a double concave, with a kind of doorway or passage from one to the other, to let the flame pass, as it were, through and round the water; by which means there is no-where above 9 inches of water to be heated through, though the boiler is so large; and which, by 3 years experience has been found to require less fuel than any other fire engine of equal size. Mr. F. fixed a pipe, of an inch and a half diameter, to a pair of double bellows 3 feet diameter; which pipe reached about 1 foot under the surface of the water in the boiler, to the end of which are fixed horizontally 2 branches, each about 8 feet long, tapering from 1 inch diameter to about of an inch. These branches are bent in a circular manner, as in the plan, to answer the form of the concave, and are perforated with small holes about 4 inches distant at the thickest part, and decreasing gradually in distance, to within of an inch towards the small end. The reason of these branches being made taper, and the distance between the holes decreasing to the small end, was in order to give the greater power to the air forced by the bellows to discharge the water lodged in such a length of pipe; and he observed by this method, that the water was gradually forced through the holes to the end of each branch, and seemed to throw an equal quantity of air through the water. The length of the pipe, to which the branches are fixed horizontally, is about 18 feet to the nosle of the bellows: and yet the steam, that passed through the pipe into the bellows, was so hot before the water boiled, as to force through the leather: but this he easily remedied, by fixing a brass cock of 14 inch diameter to the pipe, which hindered the steam from ascending, till the engine was ready to work: and being opened, the air continually keeps it cold till the engine has done working; then the cock must be shut again.

The bellows is worked by means of a small lever, and pulleys applied to the great lever of the fire-engine, which keeps a continual blast while the engine works, the strength of which is increased or diminished, by adding or taking off the weights on the bellows.

The effect produced was, first, a very visible alteration for the better in the working of the engine. When the fire was stirred, as it must be every time fuel is added, the steam generally became too fierce, which occasioned great irregularity, and sometimes, if not watched, great damage to the engine; and when the fire abated, the stroke became immediately much shorter, or stopped entirely, if fuel was not soon added, whereas, by blowing air thus through the water, it keeps, with any moderate care, an equal stroke to its full length, from the beginning to the end; and by that means discharges a considerably greater quantity of water.

As to the quantity of fuel, that may be saved by this method, it is not easy to determine from any experiment on this engine, the boiler and fire-place of which is made very different from all others, and the quantity of fuel thus greatly lessened. The fire-place, which may be said to be within the boiler, and is but barely large enough to contain a quantity of the roundest and strongest burning coals sufficient to work the engine, cannot in this be made less; and consequently will not admit such a saving from this model, as from one properly constructed for the purpose.

XI. Extract of a Letter, by Mr. Abraham Trembley, F. R. S. on Earthquakes, Polypes, Fossils, &c. Translated from the French. p. 58.

Mr. T. mentions an earthquake felt in 1756, between the Rhine and the Meuse. He was also informed by Professor Donati of Turin, that a slight shock had been perceived there on the 13th of August 1756, at a quarter after 9 in the morning. It was likewise felt in other parts of Piedmont.

He further states, that Mons. Donati took last summer, according to his custom, a journey, to prosecute his researches into natural history. He was accompanied by Dr. Ascanius, F. R. S.; who was still in doubt about coral's being a composition of animals. Mons. Donati carried him to the sea of Provence. He ordered coral to be fished up in his presence. He placed it in a large vessel full of water; and carried this vessel on shore; where he soon convinced Dr. Ascanius, by his own eyes, that coral is a mass of animals of the polype kind.

Mons. Donati also wrote that he had thoroughly satisfied himself, by his last observations, that the polypes are fixed to their cells; of which he had before doubted. What he says afterwards of coral appears to express with more truth and precision what we ought to think of this kind of animals, than any of the descriptions, which have been given since the new discoveries have changed our sentiments on that subject. Polype-beds, and the cells which they contain, are commonly spoken of as being the work of polypes. They are compared to the honeycomb made by bees. It is more exact to say that coral, and other coralline bodies, have the same relation to the polypes united to them, that there is between the shell of a snail and the snail itself, or between the bones of an animal, and the animal itself. Mons. Donati's words are as follow: "I am now of opinion, that coral is nothing else than a real animal, which has a very great number of heads. I consider the polypes of coral only as the heads of the animal. This animal has a bone ramified in the shape of a shrub. This bone is covered with a kind of flesh, which is the flesh of the animal. My observations have discovered to me several analogies between the animals of kinds approaching to this. There are, for instance, keratophyta, which do not differ from coral,

except in the bone, or part that forms the prop of the animal. In the coral it is testaceous, and in the keratophyta it is horny."

The observations which Mr. T. made on some kinds of polype-beds, led him to think that what are called polypes, in those bodies which are observed to come out of and return into the cells, are more than the heads of the animal. He had scen some which had a bag, into which passed their food, which he saw them swallow; and another bag, into which passed the grossest part of that food, after it was digested. This is the case, for instance, of the plumed polypes, which he described at the end of the 3d memoir, in the work published by him on one kind of fresh-water polypes.

Mons. Donati had observed several very curious facts in the journey which he made into the mountains. He had, in particular, traced out an immense bed of marine bodies. This bed crosses the highest mountains which separate Provence from Piedmont, and loses itself in the plains of Piedmont. He had likewise observed a mass of rock, which forms the extremity of a pretty high mountain, the foot of which is washed by the sea. This rock is, at a considerable height, entirely pierced by pholades, that species of marine shell-fish so well known, which digs cells in the stones. It hence appears, that this rock was some time covered by the sea. According to Mons. Donati, the sea has insensibly retired from the parts which were washed by it; and he thinks that there must have been a very considerable space of time between that and the time when this mountain, pierced by pholades, was covered by the waters of the sea. He deduces his opinion from the following fact. There is in this rock, pretty near the surface of the sea, a natural cavern filled with water. In this earth have been found ancient Roman sarcophagi and lamps. Hence it follows that even in the time of the Romans this part of the rock, in which this cavern is situated, was not under water. As there is but a small distance between the cavern and the surface of the water, it follows that the water has sunk but very little since the time of the Romans. If it has sunk in the same proportion since the time when it covered the top of the rock, there is no doubt but that the time when it was entirely covered by the sea, must have been very distant. If the same manner of reasoning be used with respect to the bed of marine bodies mentioned above, which crosses the mountains that separate Provence from Piedmont, we shall be obliged to presume, that the time when those mountains were under the waters of the sea, was at a very great distance from the present. Mons. Donati concludes from these facts, and the consequences deduced from them, that the Mediterranean sea is a very ancient, and not a modern one, as Mons. de Buffon imagines.

Those who explain all the phenomena of marine bodies found out of the sea, by a universal deluge, do not admit the consequences drawn by Mons. Donati from those marine bodies now under consideration. It is plain that most of the

naturalists, who have observed a great number of these marine bodies, are not of opinion that all those phenomena can be explained by a universal deluge. On these subjects, before we undertake to judge, it is proper to be well informed of the nature of marine fossil bodies, which are found in divers parts, and of their situation and arrangement. It is necessary also to be acquainted with the state of those which are found actually under the sea, and the revolutions to which they are subject, while they are covered by it. It is still further requisite to attend to the revolutions which have been, and are constantly observed, with respect to the sea-shores, which change their situation in several parts, some advancing on the land, and others retiring. If all these different facts be compared together, it will not be doubted, but there are actually under the earth marine bodies, which are found there only in consequence of these slow revolutions, and not of a universal deluge. Perhaps this notion might be extended to the greatest part of the marine fossil bodies which are known to us.

XII. A Botanical and Medical History of the Solanum Lethale, Bella-donna, or Deadly Nightshade, by Mr. Richard Pulteney. Communicated by Mr. Wm. Watson, F.R. S. P. 62.

As accurate descriptions of the deadly nightshade, or atropa belladonna, Linn. together with an account of its poisonous quality and uses in medicine, are to be found in various modern systems of botany, and treatises on the Materia Medica (the plant being a native of this country), it is deemed unnecessary to reprint this paper..

XIII. On some of the Antiquities discovered at Herculaneum, &c. By John Nixon, A. M., F.R.S. p. 88.

Mr. N. first treats of the several tali lusorii, that were played with a set of dice. Mr. N. refers to several passages in the writings of the ancients on the use of these tali. He says the tali are supposed to have been known to the Greeks by the name of 'Arrpάyaλo as early as the Trojan war. We can with certainty determine the number of the tali used in this game to have been four; and likewise, that among the various chances resulting from them, the most fortunate one was that wherein each of the sides exhibited a different aspect.

He concludes with noting, that in order to prevent any fraud or slight of hand in managing the tali, it was usual to put them into a box, and after shaking them together, to throw them out upon a table. However, this caution does not seem to have been so universally observed, but that sometimes, viz. when the party consisted of ladies, it was (he presumes, for a reason greatly to their honour) superseded. Thus, in one of the first paintings found at Herculaneum, and now in the royal apartments at Portici, a young female figure is exhibited,