"Geometriæ Pars Universalis, inserviens Quantitatum Curvarum, Transmutationi et Mensura"; in which he is allowed to have shown, for the first time, a method for the transmutation of curves. These works engaged the notice, and procured the author the correspondence of the greatest mathematicians of the age, Newton, Huygens, Wallis, and others. An account of this piece was also read before the Royal Society, of which Mr. Gregory, being returned from his travels, was chosen a member the same year, and communicated to them an account of a controversy in Italy about the motion of the earth, which was denied by Riccioli, and his followers. Through this channel, in particular, he carried on a dispute with M. Huygens, on the occasion of his treatise on the quadrature of the circle and hyperbola, to which that great man had started some objections in the course of which our author produced some improvements of his series. But in this dispute it happened, as it generally does on such occasions, that the antagonists, though setting out with temper enough, yet grew This was the too warm in the combat.

case here, especially on the side of Gregory whose defence was, at his own request, inserted in the Philosophical Transactions. It is unnecessary to enter into particulars: suffice it therefore to say that, in the opinion of Leibnitz, who allows Mr. Gregory, the highest merit for his gepius and discoveries, M. Huygens has pointed out, though not errors, some considerable deficiencies in the treatise above-mentioned, and shown a much simpler method of attaining the same end.

In 1688, our author published at London another work, entitled "Exercitationes Geometricæ," which contributed still much further to extend his reputation. About this time he was elected Professor of Mathematics in the University of St. Andrew's, an office which he held for six years. During his residence there he married, in 1669, Mary, the daughter of George Jameson, the celebrated painter, whom Mr. Wal pole has termed the Vandyke of Scotland, and who was fellow-disciple with that great artist in the school of Rubens, at Antwerp.

In 1672, he published “The great and new Art of weighing Vanity: or a Discovery of the Ignorance and Arrogance of the great and new Artist, in his pseudo-philosophical Writings. By M. Patrick Mathers, Archbedal to the University of St. Andrews.

To which are annexed some Tentamina de Motu Penduli et Projectorum." Under this assumed name, our author wrote this little piece to expose the ignorance of Mr. Sinclare, professor at Glasgow, in his hydrostatical writings, and in return for some ill usage of that author to a colleague of Mr. Gregory's. The same year Newton,

on his wonderful discoveries in the nature of light, having contrived a new reflecting telescope, and made several objections to Mr. Gregory's, this gave birth to a dispute between those two philosophers, which was carried on during this and the following year, in the most amicable manner on both sides; Mr. Gregory defending his own construction, so far as to give his antagonist the whole honour of having made the catoptric telescopes preferable to the dioptric, and showing that the imperfections in these instruments were not so much owing to a defect in the object speculum, as to the different refrangibility of the rays of light. In the course of this dispute our author described a burning concave mirror, which was approved by Newton, and is still in good esteem. Several letters that

passed in this dispute, are printed by Dr. Desaguliers, in an appendix to the English edition of Dr. David Gregory's "Elements of Catoptrics and Dioptrics."

In 1674, Mr. Gregory was called to Edinburgh, to fill the chair of mathematics in that university. This place he had held but little more than a year, when in October 1675, being employed in shewing the satellites of Jupiter through a telescope to some of his pupils, he was suddenly struck with total blindness, and died a few days after, to the great loss of the mathematical world, at only 37 years of age.

As to his character, Mr. James Gregory was a man of very acute and penetrating genius. His temper seems to have been warm, as appears from his conduct in the dispute with Huygens: and conscious perhaps of his own merits as a discoverer, he seems to have been jealous of losing any portion of his reputation by the improve. ments of others upon his inventions. He possessed one of the most amiable characters of a true philosopher, that of being content with his fortune in his situation. But the most brilliant part of his character is that of his mathematical genius as an inventor, which was of the first order; as will appear by the following list of his inventions and discoveries. Among many others may be reckoned his reflecting teles

tion of Mr. Jones and Dr. Desaguliers, and afterwards by the latter of these gentlemen; with an appendix, containing an account of the Gregorian and Newtonian telescopes, together with Mr. Hadley's tables for the construction of both those instruments. It is not unworthy of remark, that, in the conclusion of this treatise, there is an observation which shows that the construction of achromatic telescopes, which Mr. Dolland has carried to such great perfection, had occurred to the mind of David Gregory, from reflecting on the admirable contrivance of nature in combining the different humours of the eye. The passage is as follows: "Perhaps it would be of service to make the object lens of a different medium, as we see done in the fabric of the eye; where the crystalline humour (whose power of refracting the rays of light differs very little from that of glass) is by nature, who never does any thing in vain, joined with the aqueous and vitreous humours (not differing from water as to their power of refraction) in order that the image may be painted as distinct as possible upon the bottom of the eye."

In 1702, our author published at Oxford, in folio, “Astronomiæ Physicæ et Geometricæ Elementa,” a work which is accounted his master-piece. It is founded on the Newtonian doctrines, and was esteemed by Newton himself as a most excellent explanation and defence of his philosophy. In the following year he gave to the world an edition, in folio, of the works of Euclid in Greek and Latin; being done in prosecution of a design of his predecessor Dr. Bernard, of printing the works of all the ancient mathematicians. In this work, which contains all the treatises that have been attributed to Euclid, Dr. Gregory has been careful to point out such as he found reason, from internal evidence, to believe to be the productions of some inferior geometrician. In prosecution of the same plan, Dr. Gregory engaged soon after, with his colleague Dr. Halley, in the publication of the conics of Apollonius; but he had proceeded only a little way in the undertaking, when he died at Maidenhead, in Berkshire, in 1710, being the 49th year of his age.

Besides those works published in our author's life-time, as mentioned above, he had several papers inserted in the Philos. Trans. vol. xviii, xix, xxi, xxiv, and xxv, particularly a paper on the Catenarian curve, first considered by our author.

He left also, in manuscript, a short Treatise of the Nature and Arithmetic of Loga

rithms, which is printed at the end of Keill's translations of Commandine's Euclid; and a treatise of Practical Geometry, which was afterwards translated, and published in 1745, by Mr. Maclaurin.

Dr. David Gregory married, in 1695, Elizabeth the daughter of Mr. Oliphant, of Langtown in Scotland. By this lady he had four sons, of whom, the eldest, David, was appoined Regius Professor of modern history, at Oxford, by King George the First, and died at an advanced age in 1767, after enjoying, for many years, the dignity of Dean of Christ Church in that University.

When David Gregory quitted Edinburgh, he was succeeded in the Professorship of that University by his brother James, likewise an eminent mathematician, who held that office for thirty-three years, and retiring in 1725, was succeeded by the celebrated Maclaurin. A daughter of this Professor James Gregory, a young lady of great beauty and accomplishments, was the victim of an unfortunate attachment, that furnished the subject of Mallet's well-known ballad of William and Margaret.

Another brother, Charles, was created Professor of Mathematics at St. Andrew's, by Queen Anne, in 1707. This office he held with reputation and ability for thirtytwo years; and resigning in 1739, was succeeded by his sou, who eminently inherited the talents of his family, and died in

1763.

GRENADE, or GRENADO, in military affairs, a kind of small bomb or shell, being furnished with a touch-hole and fuse, and is thrown by hand from the tops, hence they are frequently styled hand-grenades. The best way to secure one's-self from the effects of a grenade, is to lie flat down on the ground before it bursts,

The grenades are of much later invention and use than the bomb. They are usually about three inches in diameter, and weigh near three pounds. The metal may be one quarter or three-eighths of an inch thick, and the hole about one-sixth.

GREWIA, in botany, so named in honour of Nehemiah Grew, M. D. F. R. S. the famous author of the "Anatomy of Vegetables," a genus of the Gynandria Polyandria class and order. Natural order of Columniferæ. Tiliacea, Jussieu. Essential character: calyx five-leaved; petals five, with a nectareous scale at the base of each; berry four-celled. There are thirteen species.

GRIAS, in botany, a genus of the Po

lyandria Monogynia class and order. Natural order of Guttiferæ, Jussieu. Essential character: corolla four-petalled; calyx fourcleft; stigma sessile, cross-shaped; drupe with an eight-furrowed nucleus. There is but one species, viz. G. cauliflora, anchovypear. This tree is about fifty feet in height, branching at the top; leaves on short petioles, pendulous, two or three feet long; flowers from the stem, on short, scaly, many-flowered peduncles. The uprightness of the growth, and the size of the leaves, give this tree a very elegant appearance. The fruit is nearly as large as an alligator's egg, resembling it very much in shape, but of a brown colour; they pickle the fruit, and eat it in the same manner with the East Indian mango, which it resembles in flavour. This beautiful tree is common in many parts of Jamaica, growing generally in low moist places.

GRIELUM, in botany, a genus of the Decandria Pentagynia class and order. Natural order of Gruinales. Essential character: calyx five-cleft; petals five; filament permanent; pericarpium five, with one seed in each. There is only one species, viz. G. tenuifolium, a native of the Cape of Good Hope.

GRIFFON, in heraldry, an imaginary animal, feigned by the ancients to be half eagle and half lion; by this form they intended to give an idea of strength and swiftness joined together, with an extraordinary vigilance in guarding the things intrusted to its care. Thus the heathen naturalists persuaded the ignorant, that gold mines were guarded by these creatures with incredible watchfulness and resolution.

GRINDERS. See ANATOMY.

GRINDING, the reducing hard substances to fine powders, either by the mortar, or by way of levigation upon a marble.

GRIPE, in the sea-language, is a piece of timber fayed against the lower piece of the stern, from the fore-mast end of the keel, joining with the knee of the head: its use is to defend the lower part of the stern from any injury; but it is often made the larger, to make the ship keep a good wind.

GRIPE is also a sea-term, for a ship's turning her head more to the wind than she should; this is caused either by overloading her a-head, the weight of which presses her down, so that she will not readily fall off from the wind; or by staying or setting her masts too much aft: which is always a fault in short ships that draw much water, since it causes them to be

continually running into the wind: though in floating ships, if the masts be not stayed very far aft, they will never keep a good wind.

GRISLEA, in botany, a genus of the Octandria Monogynia class and order. Natural order of Calycanthemæ. Salicariæ, Jussieu. Essential character: calyx fourcleft; petals four, from the incisures of the calyx; filaments, very long, ascending; capsule globular, superior, one-celled, containing many seeds. There are two species, viz. G. secunda and G. tomentosa, the latter is a beautiful flowering shrub, a native of the hills and valleys through the northern provinces of the Carnatic in the East Indies.

GRIT, a genus of argillaceous earths, with a texture more or less porous, equable and rough to the touch. It neither gives fire with steel, nor effervesces with acids. When fresh and breathed on, it exhales an earthy smell. Its specific gravity varies from 2.0 to 2.6 and is used for mill-stones and whet-stones, and sometimes for filtering-stones and building.

GROMETS, in the sea-language, small rings formerly fastened with staples to the yards, to make fast the gaskets, but now never used.

GRONOVIA, in botany, a genus of the Pentandria Monogynia class and order. Natural order of Cucurbitaceæ. Essential character: petals five, together with the stamens inserted into the bell-shaped corolla; berry dry, inferior, containing one seed. There is but one species, viz. G. scandens, climbing gronovia, an annual plant; sending out many trailing branches like those of the cucumber, closely set with broad leaves, which have a strong smell. Peduncles many flowered, axillary.

GROSS, in law-books, signifies absolute or independent on another: thus, an advowson in gross, is one distinct and separate from the manor.

GROSS BEAK, the English name of a bird called by authors loxia. See LOXIA.

GROSS weight, the whole weight of merchandizes, with their dust and dross: as also the bag or chest wherein they are contained. An allowance is usually made out of the gross-weight for tare and tret. See TARE.

GROTTO, a large deep cavern or den in a mountain or rock. Okey-hole, Eldenhound, Peake's-hole, and Pool's-hole, are famous among the natural caverns or grottos of our country. The entrance to Okey-hole, on the south side of Mendip