by viewing the southern cross, and observing at what hour it shall appear perpendicular to the horizon, or rather, when the time will permit, by observing with the plumb line held in the hand the very moment when the stars in the foot, and a in the head of the southern cross appear equally distant from the perpendicular, the latter on the east side, the former on the west: for at the point of time when this happens, there will hardly be an error of 1 minute of the truth, if 15 minutes be added to the hour of mediation of the first point of Aries; which will be determined by the above-mentioned table, the difference of the meridians of the calculator and observer being amended.

Of two Beautiful Echinites. By Mr. E. da Costa, F.R.S. N° 492, p. 143. These 2 echinites are undoubtedly moulded in shells, of a genus of which we at present find some species now living in the seas; mostly in the West Indies. The echinometra of Aristotle, Aldrovand, and of Dr. Grew, is of this genus. Dr. Breyn calls the whole genus echinanthus; and Mr. Klein, scutum. Woodward, in his distribution of fossil echini, calls them the pentaphylloides, from the rays on the upper part forming a beautiful cinquefoil figure; but erroneously fixes their characteristics in having only one aperture, and that at the basis; in which he not only contradicts nature, but also the very specimens he quotes in his own collection, which have all two foramens or apertures, and are elegantly figured so by Agostino Scilla, who was the person that sent them to the doctor; and our late president Sir Hans Sloane has also figured and described 2 species of this genus, one species of which is an inhabitant of our English seas.

No author has ever described echinites, or stones moulded in the fossil echini of this genus; nor even have the fossil echini or shells themselves been ever exhibited by any lithologist, except by the above-quoted A. Scilla, who found them in Malta, sent them to Dr. Woodward, and to which the doctor in his catalogue recounts 2 other specimens, which were dug up in Maryland; so rare are the instances of the fossils of this whole genus! The 2 echinites here described were all found in the midst of some rocks, which were blown up at Port Mahon some years before, and whence they were all brought.

The first or largest is composed of a hard or stony arenaceous greyish substance, and is of an escutcheon or heart-like shape: it measures about 144 inches in circumference, or quite round the limb or edge, about 2 inches high from the flat or basis, to the tip of the apex, 5 inches in length at the basis, and 44 in breadth. On the upper part it rises nearly gradually from the edge quite to the apex. A central point, with a slight declining space, tops the said apex; from which space the body regularly divides into 5 parts figured like leaves to the edge. These leaves are narrow at the apex, greatly widen towards the bottom,

and narrow a little again at their end. Each division or leaf is bounded on each side by a row of parallel ridges, which are accompanied also on each side of every said row, with 2 other ranges of points or knobs; all which rows do not meet or close together at the lower end of the division, but leave a void unwrought space: a row of larger irregular knobs runs through the midst of each leaf. From the divisions between each leaf runs a rugged knobb'd pillar, joined to the edge: the other parts between the leaves and the edge, are hollows, or void spaces. The edge or limb is of a thick cylindric make, runs quite round the whole body, and only has some signs of being disjoined at the one extreme of the length, or where the aperture was; the stone answering which is here extended a little cylindri– cally outward like an appendage, and was so formed by the stony matter being too much in quantity for the shell, and so was protruded through the said foraOn the outer edge of the limb, are some few irregular stony concretions. The basis is flat, and is divided into 5 parts from the centre, which is one of the foramens; the other foramen being placed at one of the extremes of the length. This foramen or centre is about the size of a shilling. The 5 divisions extend to the utmost edge of the body, or quite over the limb, contrary to the divisions on the upper part, which extend only to it. Each division is formed by a stony line edged on each side with stony cylindrical bodies of the thickness of a pin, but of different lengths, so as to appear like the teeth of a comb, or the gills of a fish; the interstices between all which is a rugged stony work, and hollows pervading quite through the body to the upper part,

The other echinite is of a different species, though of the same genus, of a heart-like shape, and about one third the size of the above described. This is greatly copped, the apex lying very high, and the 5 divisions running nearly perpendicular down to the edge. The upper part of this is elegantly perfect; the work is nearly the same as on the other; only that, by the perfection this preserved is in, we observe that the rows of parallel ridges, which adorn each side of each leaf or division, rise into a kind of arched work or bridge, made up of arched cylindrical bodies, through which the middle row runs, joined or connected in a long straight cylindrical stem, in a most curious and elegant manner. The basis or under part of this specimen is very imperfect, and only seems to differ in the centre being greatly excavated or concave, answering to the great copping or height of the apex or upper part. This fossil also consists of a hard stony arenaceous substance like the other.

From the inspection of the several hollows of these echinites, it is evident that they were not immediately moulded in the shells, but were formed in cavities which those shells formerly filled in the rocks they were lodged in. The rocks were apparently of a loosened arenaceous texture, and the water, &c. continually pervading them, rotted and destroyed the inclosed shells, and bore

their whole substance. In the same manner, and by the same means, away were the stony particles replaced into those very cavities which the shells formerly filled; consequently these bodies were moulded exactly to the said cavities.

This remark carries a conclusion with it, that the hollows and solid parts of these stones exactly answer to the hollows and solid parts of the very shells themselves; which, had they been moulded in the very shells, must have happened directly contrary; the solid parts of the shells forming hollows in the stone, and vice versa. In all sandy or lax earthy matter, fossil shells are very seldom found, but only the moulded stones; the loose texture of those substances giving free access to water, vapours, and mineral exhalations, &c. which entirely corrode and destroy the shells buried in it.

The State of the Tides in Orkney. By Mr. M. Mackenzie.*

N° 492, p. 149.

There is little or nothing uncommon in the manner of these tides. Ordinary spring tides rise 8 feet perpendicular, ordinary neap tides 3; extraordinary high spring tides rise 14 feet; extraordinary low, only 5; extraordinary high neap tides rise above 6 feet; extraordinary small neap tides not above 2. Low water neap tide, at a mean, is about 3 feet above low water spring tide, and high water spring tide about 3 feet above high water neap tide.

On the coast of Orkney, and fair isle of Shetland, the body of the flood comes from the north-west; on the east and west coasts of Lewis, one of the western isles of Scotland, it comes from the south. A league or two off the coast, the strength of the stream is scarcely sensible, except when it is confined by land, or near rocks or shoals. When the tide begins to rise or fall on the shore, about that same time the stream near the shore begins to turn or reverse its direction, a few irregularities excepted.

The stream of tide changes its direction sooner near land than at a distance from it; insomuch that, in a place 2 or 3 miles from land, the turning of the tide is 2 hours, or more, later than on the adjacent shore: at intermediate distances the streams turn at intermediate times. Hence a vessel may find a favourable tide near land, while it would be against her a mile or two from it; and the contrary.

During the continuance of flood, the stream varies its direction gradually from the east towards the south, and the stream of ebb from the west towards the north that is, if the stream, when it becomes first sensible, runs east, at the latter end of the tide it will run south, if the proximity of land or shoals does not hinder this change of direction.

*Author of a treatise on Maritime Surveying, printed 1774, in 4to.

The greatest velocity of spring tide in Orkney, in the channels where it runs quickest, is about 9 miles an hour: the greatest velocity of neap tide is about one third or fourth of spring tide. The tides are most rapid commonly between the third and fourth hour. Spring tides acquire a considerable degree of strength in less than one hour after their quiescent state begins; neap tides are hardly sensible in 2 hours after.

Some Account of the Remains of John Tradescant's* Garden at Lambeth. By Mr. W. Watson, F.R.S. N° 492, p. 160.

Upon a visit made to Mr. John Tradescant's garden at South Lambeth, May 21, 1749, by Dr. Mitchell and Mr. Watson, were observed the under-mentioned exotic plants.

"John Tradescant (says Dr. Pulteney, in his work entitled "Historicul and Biographical Sketches of the Progress of Botany in England,") was by birth a Dutchman, as we are informed by A Wood. On what occasion, and at what period he came into England, is not precisely ascertained. He is said to have been for a considerable time in the service of Lord Treasurer Salisbury, and Lord Wotton. He travelled several years, and into various parts of Europe; as far eastward as into Russia. He was in a fleet that was sent against the Algerines in 1620, and mention is made of his collecting plants in Barbary, and in the isles of the Mediterranean. He is said to have brought the trifolium stellatum Lin. from the island of Fermentera; and his name frequently occurs in the second edition of Gerard, by Johnson; in Parkinson's Theatre of Plants, and in his Garden of Flowers, printed in 1656. But I conjecture, that Tradescant was not resident in England in the time of Gerard himself, or known to him. He appears however to have been established in England, and his garden founded at Lambeth; about the year 1629, he obtained the title of gardener to Charles the First. Tradescant was a man of extraordinary curiosity, and the first in this country who made any considerable collection of the subjects of Natural History. He had a son of the same name, who took a voyage to Virginia, from whence he returned with many new plants. They were the means of introducing a variety of curious species into this kingdom; several of which bore their name. Tradescant's spiderwort, Tradescant's aster, are well known to this day; and Linnæus has immortalized them among the Botanists, by making a new genus, under their name, of the spiderwort, which had before been called ephemeron. His museum, called Tradescant's ark, attracted the curiosity of the age, and was much frequented by the great, by whose means it was also much enlarged, as appears by the list of his benefactors, printed at the end of his Museum Tradescantianum; among whom, after the names of the king and queen, are found many of the first nobility. This small volume the author entitled " Muscum Tradescantianum, or a Collection of Rarities preserved at South Lambeth, near London, 1656," 12mo. It contains lists of his birds, quadrupeds, fish, shells, insects, minerals, fruits, artificial and miscellaneous curiosities, war instruments, habits, utensils, coins, and medals. These are followed by a catalogue, in English and Latin, of the plants of his garden, and a list of his benefactors. Prefixed to this book were the prints of both father and son, which, from the circumstance of being engraved by Hollar, has rendered the book well known to the collectors of prints, by whom most of the copies have been plundered of the impressions. In what year Tradescant died is not certain, but his print represents him as a man advanced in age. The son inherited the museum, and bequeathed it by a deed of gift to Mr. Ashmole, who lodged in Tradescant's house. It afterwards became part of the Ashmolean Museum, and the name of Tradescant was unjustly sunk in that of Ashmole. John, the son, died in 1662. His widow erected a a curious monument, in memory of the family, in Lambeth church yard."

This garden was planted by the above-mentioned gentleman about 120 years before, and was, except that of Mr. John Gerard, the author of the Herbal, probably the first botanical garden in England. The founder, after many years spent in the service of the Lord Treasurer Salisbury, Lord Wotton, &c. travelled several years, and procured a great variety of plants and seeds before not known in England; to several of which at this time the gardeners give his name, as a mark of distinction; as Tradescant's spiderwort, Tradescant's aster, Tradescant's daffodil. He first planted here the Cupressus Americanus Acacia foliis deciduis, which has been since so much esteemed, and is now one of the great ornaments of the Duke of Argyle's garden at Witton.

Mr. Tradescant's garden has now been many years totally neglected, and the house belonging to it empty and ruined; and though the garden is quite covered. with weeds, there remain among them manifest traces of its founder. We found there the Borrago latifolia sempervirens of C. B. Polygonatum vulgare latifolium C. B. Aristolochia clematitis recta C. B. and Dracontium Dod.. There are yet remaining two trees of the arbutus, the largest he has seen; which, from their being so long used to our winters, did not suffer by the severe colds of 1729 and 1740, when most of their kind were killed throughout England. In the orchard there is a tree of the rhamnus catharticus, about 20 feet high, and near a foot in diameter, by much the greatest he ever saw.

On the Acceleration of the Moon. By the Rev. Richard Dunthorne.* N° 492, p. 162.

After comparing a good number of modern observations, made in different situations of the moon and of her orbit, in respect of the sun, with the New

"The Museum Tradescantianum, says Mr. Pennant, in his History of London, is a proof of the industry of the Tradescants. It is a catalogue of their vast collection, not only of the subjects. of the 3 kingdoms of nature, but of artificial rarities from a great variety of countries. The col-lection of medals, coins, and other antiquities, appears to have been very valuable. Zoology was in: their time but in a low state, and credulity far from being extinguished: among the eggs is one supposed to have been the egg of the dragon, and another of the griffin. You might have found here two feathers of the tail of the phenix, and the claw of a ruck, a bird able to truss an elephant.. After his death, which happened about the year 1652, his collection came into the possession of the famous Mr. Elias Ashmole, by virtue of a deed of gift which Mr. Tradescant jun. had made to him of all his varieties, in true astrological form, being dated December 16, 1657, 5 hours 30 minutes, post merid."

• Rd. Dunthorne was born in the year 1711, at Ramsey, in Huntingdonshire. While very young he contracted a thirst for learning by reading some old magazines, which his father, who was a gardener, used for the purposes of wrapping up seeds, &c. Being sent to the free grammarschool of his native place, he so distinguished himself, as to gain the notice of his superiors, among whom was Dr. Long, master of Pembroke Hall, Cambridge, who afforded him great encouragement; and at length removed him to Cambridge as his foot-boy. In the short time he remained in