Philosophical transactions, Vol. L. Part I. For the year 1757. · Various
PEYSSONEL. LEMOINE. MOULON.
A second visitation was made in October 1748. VIII. _An Account of the late Discoveries of Antiquities at_ Herculaneum; _in an Extract of a Letter from_ Camillo Paderni, _Keeper of the_ Herculanean Museum, _and F.R.S. to_ Thomas Hollis, _Esq; dated_ Naples, Dec. 16, 1756. [Read Feb. 10, 1757.] IT is probable, that the first volume of antique paintings will be published at Easter; in which there will be fifty copper-plates, with observations by the academy lately established here for illustrating the antiquities. Two volumes of the ancient papyrus have been unrolled. One treats of _rhetoric_, and the other is upon _music_; and both are written by the same author, Philodemus. Il Signor Canonico Mazzocchi, a very learned gentleman of this city, is now translating them from the Greek. There are two persons constantly employed in unrolling other volumes. In the month of April were found two fine busts of women, the subjects unknown. Also a young stag, of excellent workmanship, upon a base. The height of it, from the feet to the top of the head, is three palms and a half. Likewise its companion; but broken in many pieces; which however I hope to restore. In May, a small young hog.
In October, a female statue, of middling workmanship. Also a Silenus, a palm and three inches high, standing upon a square base raised upon three rows of steps, which are supported at the angles by lions claws. He has a bald head, a long curled beard, a hairy body, and naked feet. The drapery about him is loose and flowing: the fore-finger of each hand is extended, and all the rest are closed. From his back arises a branch above the head, where it divides into two, which, twisting their foliage round it, fall and spread themselves below the shoulders, on each of which a stand is placed to fix a lamp. In the middle, betwixt the extremities of these two small branches, is a bird resembling a parroquet. The whole of this figure is in a very good taste. All these things above-mentioned are of bronze. In November was discovered a beautiful marble Terminus, of Greek workmanship, as big as the life. It is drest in a chlamys; has a young countenance; and the head is covered with a Grecian helmet. Many other things have also been found, as lamps, vases, and such-like, in bronze. And we have often met with paintings. If any farther discoveries are made, which are remarkable, you may depend on being informed of them.
BEING an airing the other day with Mrs. Borlase, on the sands below my house, we perceived the sands betwixt the Mount and Penzance much washed into pits, and bare stony areas, like a broken causey. In one of the latter, Mrs. B. as we passed by, thought she saw the appearance of a tree; and, upon a review, I found it to be the roots of a tree, branching off from the trunk in all directions. We made as much haste down to the same place in the afternoon as we could, and with proper help to make a farther examination. I measured and drew the remains; and about 30 feet to the west found the roots of another tree, but without any trunk, tho’ displayed in the same horizontal manner as the first. Fifty feet farther to the north we found the body of an oak, three feet in diameter, reclining to the east. We dug about it, and traced it six feet deep under the surface; but its roots were still deeper than we could pursue them. Within a few feet distance was the body of a willow, one foot and a half in diameter, with the bark on; and one piece of a large hazel-branch, with its bark on.
What the two first trees were, it was not easy to distinguish, there being not a sufficiency remaining of the first, and nothing but roots of the second, both pierced with the teredo, or augur-worm. Round these trees was sand, about ten inches deep, and then the natural earth, in which these trees had formerly flourished. It was a black marsh-earth, in which the leaves of the juncus were intirely preserved from putrefaction. These trees were 300 yards below full-sea-mark; and, when the tide is in, have at least 12 feet of water above them: and doubtless there are the remains of other trees farther towards the south, 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 my letter to you, p. 92; and the different levels and tendencies, which we observed in the positions of the trees we found, afford us 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 are 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. I am, Sir, Your most affectionate and obliged humble Servant, Wm. Borlase. X. _Experiments on applying the Rev. Dr._ Hales’_s Method of distilling Salt-water to the Steam-Engine. By_ Keane Fitzgerald, _Esq; F.R.S._ [Read Feb. 17, 1757.] ON reading Dr. Hale’s account of purifying salt-water, by blowing showers of air thro’, it occurred to me, 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, by the best experiments hitherto made, has never been found above ⅒ stronger, or weaker, than air; I was in doubt, whether steam, produced by this method, would be sufficiently strong for the purpose of the steam-engine. I 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 thro’; the aperture of which was covered with a thin plate, fixt 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 six inches. From the best observation I was capable of making with this machine, by blowing air thro’ the boiling water, it produced about ⅙ more steam than was produced by the same fire without blowing air thro’.
I then applied a machine of this kind to the engine at the York-buildings water-works, the boiler of which is 15 feet diameter. This is a patent-boiler, a section and plan of which is annexed. It has a double concave, with a kind of door-way or passage from one to the other, in order to let the flame pass, as it were, thro’ and round the water; by which means there is no-where above nine inches of water to be heated thro’, tho’ the boiler is so large; and which, by three years experience, has been found to require ¼ less fuel, than any other fire-engine of equal bigness. I fixt a pipe of an inch and a half diameter to a pair of double bellows three feet diameter; which pipe reached about one foot under the surface of the water in the boiler; to the end of which are fixed horizontally two branches, each about eight feet long, tapering from one inch diameter to about ¼ 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 four inches distant at the thickest part, and decreasing gradually in distance, to within ¼ 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 I observed by this method, that the water was gradually forced thro’ the holes to the end of each branch, and seemed to throw an equal quantity of air thro’ the water.
The length of the pipe, to which the branches are fixed horizontally, is about 18 feet to the nosle of the bellows: notwithstanding which length, the steam, that passed thro’ the pipe into the bellows, was so hot before the water boiled, as to force thro’ the leather: but this I easily remedied, by fixing a brass cock of one inch and a half diameter to the pipe, which hindered the steam from ascending, until the engine was ready to work; and being opened, the air continually keeps it cold until the engine has done working; then the cock must be shut again. The bellows is worked by means of a small lever, and pullies applied to the great lever of the fire-engine, which keeps a continual blast whilst the engine works; the strength of which is increased or diminished, by adding or taking off the weights on the bellows.
The effect produced, according to the best observations I could make, 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 intirely, if fuel was not soon added: whereas, by blowing air thus thro’ 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. A proof of which was very evident, tho’ I could not ascertain the exact quantity: for the engine, before this improvement, supplied but two main pipes at once, which conveyed the water to the houses served by them; but since could not take off the quantity of water thrown up, part of which was obliged to be discharged into a third main.
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 already thereby 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: a proof of which I made, by trying some coals of a weaker kind, which were also cheaper; but on trial were not strong enough to work the engine, and had therefore been laid by. These coals answered extremely well; and, as it was a slower-burning coal, I found the consumption, whilst they lasted, was between two and three bushels less in every six hours, which is about the time the engine works each day: and I am satisfied, if the person, who attends the engine, would take the proper care, more coals could still be saved. For at several different times, when I had the coals exactly measured, and marked the time, I constantly found, that it required half a bushel in the hour less than he generally used, and the engine threw up as much water. As this method of blowing air thro’ boiling water, in order to increase the quantity of steam for a fire-engine, has, I believe, never before been attempted, and produces already a very good effect, I am in hopes it may be still further improved. XI. _Extract of a Letter of Mr._ Abraham Trembley, _F.R.S. to_ Tho. Birch, _D.D. Secret. R.S. Translated from the_ French. [Read Feb. 17, 1757.] Hague, 1 Feb. 1757.
Text from Project Gutenberg, public domain in the United States.