thread in a hundred coarser than the guide-screw H. The wheels on the guide-screw arbor H, and that on the steel E, on which the screw was to be cut, were proportioned to each other to produce that effect, by giving the wheel L 193 teeth, and the wheel Q 200. These wheels communicated with each other by means of the intermediate wheel R, which also served to give the threads on the two screws the same direction.

"The saddle-piece P is confined on the bar A by means of the pieces (g), and may be made to slide with a proper degree of tightness by the screws (n)."

For Ramsden's equatorial or portable observatory, see Optics, no 102, and Astronomy, no 504. See also a long account of an equatorial instrument made by Mr Ramsden by the direction of Sir George Shuckburgh in the Philosophical Transactions for 1793, art. x. p. 67. In this instrument the circle of declinations is four feet in diameter, and may be observed nearly to a second. The glass is placed between six pillars, which form the axis of the machine, and turn round by two pivots placed on two blocks of stone. See also Barometer.

a town of Huntingdonshire, 68 miles north of London, and 12 north-east of Huntingdon. It is situated as it were in an island, being everywhere encompassed with seas, except on the west, where it is separated from the terra firma by a causeway for two miles. The neighbouring waters of Ramsey and Whitley, which are formed by the river Nene, abound with fowl and fish, especially eel and large pikes. It was once famous for a very rich abbey, part of the gatehouse of which is still standing, and a neglected statue of Alwin; the epitaph of whose tomb, which is reckoned one of the oldest pieces of English sculpture extant, styles him "kinsman of the famous King Edward, alderman of all England, and the miraculous founder of this abbey." It was dedicated to St Dunstan, and its abbot was mitred, and fat in parliament; and so many kings of England were benefactors to it, that its yearly rents, says Camden, were 7000l. The town was then called Ramsey the Rich; but by the dissolution of the abbey it soon became poor, and even lost its market for many years, till about 185 years ago it recovered it. It is held on Saturday, and is reckoned one of the most plentiful and cheapest in England. In the year 1721 a great number of Roman coins was found here, supposed to have been hid by the monks on some incursion of the Danes. There is a charity school in the town for poor girls. W. Long. o. 19. N. Lat. 52° 26'.

an island of south Wales, on the coast of Pembrokehire, about two miles in length, and a mile and a half broad. Near it are several small ones, known by the name of the bishop and his clerks. It is four miles west of St David's, and 17 north-west of Milford haven. It belongs to the bishopric of St David's, and was in the last age, says Camden, famous for the death of one Julianus, a most holy man, who retiring hither from Britain, in that age rich in saints, and devoting himself entirely to God, lived a long while in solitude, and being at last murdered by his servant was enrolled among the martyrs. W. Long. 5° 20'. N. Lat. 51° 55'.