THE

PHILOSOPHICAL TRANSACTIONS

OF THE

ROYAL SOCIETY OF LONDON;

ABRIDGED.

XCVI. Of an Unusual Agitation of the Sea, at Ildfracombe, in Devonshire, Feb. 27, 1756. By the Rev. Mr. Prince of Barnstable. P. 642.

On Friday, Feb. 27, 1756, at 6 in the evening, the weather being then extremely fair, as it had been for some time before, and continued for some days afterwards, the sea being exceedingly calm, a rumbling noise was heard like that which usually precedes what the sailors call a ground sea, only it was much. louder. The tide, at that time, was above half ebbed, and retired as far as the head of the key, leaving the vessels within the pier on dry ground; when on a sudden the sea came on with a great run, filling the quay to the height of 6 feet perpendicular; and the water remained at the same height near half an hour, but was all the time agitated as in a storm. The like phenomenon also happened Nov. 1st, last year, and the waters then rose to the same perpendicular height.

XCVII. Extract of a Letter from the Rev. Mr. Holdsworth, at Dartmouth, relating to the Agitation of the Waters observed there Nov. 1, 1755. p. 643. There was a surprizing agitation in the waters about 9 in the morning of Nov. 1, 1755, when there was a great and sudden swell, though there was but little wind. During this fermentation, though it was 4 hours ebb, the waters rose as high, or higher than they usually do on the highest spring tide. This violent motion lasted about of an hour, and then the waters fell to their usual height at that time of the tide.

XCVIII. A Method of Observing the Wonderful Configurations of the Smallest Shining Particles of Snow, with several Figures of them. By John Nettis, M. D., Middleburg, &c. Translated from the Latin. p. 644.

The weather being intensely cold in the year 1740, the snow which fell was

hard, entire, and pellucid, and some particles being received on a pencil, were placed on a plane glass plate under the object glass of the best microscopes: the greatest care was taken that the smallest particles might not be dissolved, either by the breath or perspiration of the hands, lest the little angles might by the least degree of warmth disappear. And thus, with this apparatus and these precautions, the extreme exactness and equality of the figures of their most minute particles might be observed and delineated.

Some consisted of long round spicule; others approached to a round figure made up of small globules; but these were observed to be opaque, as the air was disposed to thaw; but when the air was frosty, many slender hexangular figures appeared, some of equal, others of unequal sides; such as are exhibited by Scheuchzer in his Herbarium Diluvianum, and by Swedenburg in his Prodromus Principiorum, p.21; and such as I have seen in a pitcher, which was covered, in which the water was frozen; and such figures of the concretions of vitriol, salts, &c. as may be seen in the works of Leuwhenhoek, whom I find to be the most faithful and expert in delineating and describing the minutest natural bodies; and also such as are published by Capellar in his Prodromus Crystallographiæ.

Several little stars seemed to consist of 6 oblong, round, hexangular lamellæ, or indeed of 6 rays terminating in points; which little stars appeared to be formed of 6 plane rhomboidal particles. Several plane hexangular particles of equal sides, or oblong hexangulars, adhered to several of these stars, either at their extremities, or at each side of every ray. Some hexangular lamellæ of equal sides were adorned all round with 6 other lamellæ of the same figure and size, or with hexangular oblong lamellæ, and to these sometimes adhered several others, more or less. Many of these hexangulars were ornamented with 6 rays, and to these were fixed the most slender lamellæ, which were also hexangular, of equal or unequal sides: but of equal angles of 60 degrees; and to these lamellæ others like them adhered, some greater and some less, but most of the latter; and various others like the fortifications of cities appeared to be joined to long hexangular spiculæ, and plane hexangles of equal sides. In one day and night he found 15, 20, or more particles of snow differently formed; such as Olaus Magnus mentions; and in the year 1740, on the 11th, 12th, 13th, 21st, and 23d of January, and also on the 6th, 23d, and 24th of February, he had an opportunity of delineating 80 different admirable figures of snow, and of observing their numberless varieties.

And though a vast variety of these configurations of snow may fail or vanish in the same moment, yet the smaller particles, from their various combinations with each other, constituting this wonderful variety of configurations of the snow, were observed by him to be comprehended under these following forms; viz. of parallelograms, or oblong, straight, or oblique quadrangles, rhombs, rhomboids, trapezia, or of hexangular forms of equal or unequal sides, whose

angles are 60 degrees: and these hexangular particles were far more numerous than those of any other form.

The natural size of most of the shining quadrangular particles, and of the little stars of snow, as well the simple as the less compound ones, does not exceed the 20th part of an inch: nor do the more compound particles the 5th of an inch. For the natural magnitude, or rather smallness, see pl. 1, where these beautiful various configurations are exhibited, to the number of 91. N° 57 and 84 are anomalous figures of snow; of which there is an infinite variety, that may be observed.

XCIX. Of the Copper-springs lately discovered in Pennsylvania. By John Rutty, M.D. of Dublin. P. 648.

In the province of Pennsylvania is a copper mine, which affords a spring that appears to have the same qualities as that Irish water lately described by Dr. Wm. Henry and Dr. Bond, in the 47th and 48th volumes of the Philos. Trans., but is much sharper, for it will dissolve iron in a quarter part of the time; and we are assured, by the accounts transmitted from the proprietors of it, of the trials they have made, that it yields the same copper-mud or dust as our Cronebaun-water, of the county of Wicklow, which being collected from bars of iron immersed in it, for the purpose of extracting the copper from the Pennsylvania water, it produced above half pure copper on being melted in a crucible; an experiment that requires to be repeated in order to ascertain the proportion of copper contained with accuracy; our copper-spring of the county of Wicklow yielding a proportion considerably larger than this, viz. 16 parts of copper out of 20 of the mud.

In the neighbourhood is a great abundance of the ores of vitriol and sulphur, and the spring comes through an immense body of vitriol-ore, and the supply of water is very large, 700 or 800 hogsheads flowing in 24 hours.

taste

The water is of a pale-green colour, of an acid, sweet, austere, inky and nauseous It is very ponderous, and instantly betrays the great strength of the metallic impregnation by the hydrometer; which, immersed in this water, presently mounted above the ball, and stood in it nearly at the same height as in a solution of one oz. and six drams of English vitriol in a quart of water. A little of the solution of pot-ashes instantly precipitates the metallic parts of this water, in grains of 3 different colours, viz. ochre-coloured at the top, green in the middle, and white at the bottom: and the appearances with spirit of hartshorn were much alike, except that the grumes at the bottom participated of a mixture of a blue colour with the white, indicating more clearly the mixture of copper.

But iron immersed, above all other things, renders the contained copper conspicuous to the eye; for a clean knife, kept in it a few minutes, is covered with

a bright copper-colour; and needles and nails kept immersed in it a month in a phia! are covered with a rust, partly yellow and shining, which seems to be the copper, and partly a ferrugineous matter, as appeared by the magnet: and that it was partly cupreous appeared by the bright blue tincture extracted by spirit of hartshorn from such parts of the rust as did not readily fly to the magnet; and, if one might rely on the Philadelphia experiment above-mentioned, the proportion of copper should be very large.

It is however certain, that as in other copper-springs, so in this, here is a very considerable proportion of the vitriol of iron combined with it, and by all experiments a much greater than of the vitriol of copper; and accordingly, galls added to this water turned it first blue (the characteristic of martial vitriol) and then of a dilute ink-colour; and the corks in the bottles were blackened. But the genuine quality, as well as a large proportion, of the impregnating salt, will further appear by the following analysis of this water, viz. a pint of it, exhaled by a slow fire, left 400 grains of solid contents, which were partly green and partly ochre-coloured, with an intermixture of bluish, and of a rough, sweetish taste, like that of sal martis, and appeared to be chiefly saline, not leaving above 4 grains of indissoluble matter on dissolving 196 grains of it, and filtring.

Thus it appears, that the proportion of vitriolic parts in this water is very large, viz. above 6 drams to a pint or 3200 grains to a gallon; and consequently it is a stronger solution of vitriol than sea-water is of marine salt; and is considerably the strongest of all the vitriolic waters, that have yet occurred to my observation; for our Cronebaun water, in the county of Wicklow, gives but 256 grains from a gallon; Haigh in Lancashire, (the strongest in Britain, that I know of) 1920 grains; Shadwell 1320; Kilbrew, in the county of Meath, 1530 from the same quantity; so that besides the copper to be obtained by immersing bars of iron, as in our county of Wicklow water, this water offers to its proprietors another peculiar advantage, viz. an opportunity of erecting a copperas-work or manufacture of vitriol, like the Hungarian vitriol; especially the vast supply of water and plenty of fuel in the place considered.

C. Extract of a Letter from the Abbé Mazeas, F.R.S. concerning an Ancient Method of Painting, Revived by Count Caylus.* Translated from the French by James Parsons, M. D., F. R. S. p. 652.

The Count de Caylus, a member of the Academy of Inscriptions, had under

* A celebrated French antiquary, author of a splendid work entitled Antiquités Egyptiennes, Etrusques, Grecques, Romaines et Gauloises, in 7 vols. 4to. The last vol. contains an éloge of the author, by Mons, le Beau. He was a great encourager of artists, and wrote the Lives of several Painters and Engravers to the French Academy. In addition to the works just mentioned, there are many learned dissertations by this author in the Memoirs of the Academy of Inscriptions. Count Caylus died in 1765, in the 73d year of his age.

taken to explain an obscure passage in Pliny the naturalist. This author says in some place of his works, that "the ancients painted with burnt wax;" and we have it from tradition, that pictures of this kind were very durable. This was the passage, that the count undertook to clear up, by trying all the different ' ways possible to paint in wax; and after many experiments he hit upon a very simple method, of which he made a secret, in order to excite the curiosity of the public. For that time he only thought proper to show one picture at the Louvre, representing the head of Minerva, painted in the manner of the ancients, and which was much admired.

The several artists, who were desirous of knowing by what means the count came to make this discovery, made several attempts themselves; but in a great number of trials, only 2 are worth mentioning.

The first was to melt wax and oil of turpentine together, and use it for mixing the colours. But this method does not at all explain Pliny's meaning, because wax is not burnt in this way of managing it: and besides, this method has two defects; the oil of turpentine dries too fast, and does not allow the painter sufficient, time to blend and unite his colours. The 2d method is very ingenious, and seems to come up to Pliny's notion very well: it is as follows: the wax is melted with strong lixivium of salt of tartar, and with this the colours are ground. When the picture is finished, it is gradually put to the fire, which increases the heat by degrees; the wax melts, swells, and is bloated up upon the picture: then the picture is removed gradually from the fire, and the colours do not at all appear to have been disordered: the colours then become unalterable by the action of the air, and even spirit of wine has been burnt upon them without doing them the least harm.

However, the following is the Count de Caylus's method, which is much more simple; according to which the head of Minerva was painted, which was so much admired by all the connoisseurs. 1st. The cloth or wood, designed for the picture, is waxed over, by only rubbing it simply with a piece of bees-wax. 2dly, The colours are mixed up with common water; but as these colours will not adhere to the wax, the whole picture is to be first rubbed over with the Spanish white, and then the colours are used. 3dly, When the picture is dry, it is put near the fire, by which the wax melts, and absorbs all the colours. The effect produced by these colours upon wax is very singular; nor can one have any notion of it without seeing it. The colours have not that natural varnish or shining that they acquire with oil; but you are capable of seeing the picture in any light, or in whatever situation you place it: in short there can be no false glare or light on the picture for the spectators: the colours are secured, are firm, and will bear washing; and have a property, that they have smoked this picture in places subject to foul vapours, and to smoke in chimnies; and then by being exposed to the dew, it became as clean as if it had been but just painted.