improved by Dolland, Troughton, and others.  Near it is a curious transit-clock, made by Graham, but greatly improved by Earnshaw, who so simplified the train as to exclude two or three wheels, and also added cross-braces to the gridiron-pendulum, by which an error of a second per day, arising from its sudden starts, was corrected.  The quadrant-room has a stone pier in the middle, running north and south, having on its east face a mural-quadrant, of eight feet radius, made by Bird, in 1749, by which observations are made on the southern quarter of the meridian, through an opening in the roof three feet wide, produced by means of two sliding shutters; on its west face is another eight-feet mural quadrant, with an iron frame, and an arch of brass, made by Graham, in 1725:  this is applied to the north quarter of the meridian.  In the same apartment is the famous zenith-sector, twelve feet in length, with which Dr. Bradley, at Wanstead, and at Kew, made those observations which led to the discovery of the aberration and nutation:  here also is Dr. Hooke’s reflecting telescope, and three telescopes by Harrison.  On the south side of this room is a small building, for observing the eclipses of Jupiter’s satellites, occultations, &c., with sliding shutters at the roof and sides, to view any portion of the hemisphere, from the prime verticle down to the southern horizon:  this contains a forty-inch achromatic, by the inventor, Mr. John Dolland, with a triple object-glass, a most perfect instrument of its kind; and a five-feet achromatic, by John and Peter Dolland, his sons.  Here, likewise, are a two-feet reflecting-telescope (the metals of which were ground by the Rev. Mr. Edwards), and a six-feet reflector, by Dr. Herschell.

The lower part of the house serves merely for a habitation; but above is a large octagonal room, which, being now seldom wanted for astronomical purposes, is used as a repository for such instruments as are too large to be generally employed in the apartments first described, or for old instruments, which modern improvements have superseded.  Among the former is a most excellent ten-feet achromatic, by the present Mr. Dolland, and a six-feet reflector, by Short, with a clock to be used with them.  In the latter class, besides many curious and original articles, which are deposited in boxes and cupboards, is the first transit instrument that was, probably, ever made, having the telescope near one end of the axis; and two long telescopes with square wooden tubes, of very ancient date.  Here, likewise, is the library, which is stored with scarce and curious old astronomical works, including Dr. Halley’s original observations, and Captain Cook’s Journals.  Good busts of Flamstead and Newton, on pedestals, ornament this apartment; and in one corner is a dark narrow staircase, leading to the leads above, whence the prospect is uncommonly grand; and to render the pleasure more complete, there is, in the western turret, a camera obscura, of unrivalled excellence, by which all the surrounding objects, both movable and immovable, are beautifully represented in their own natural colours, on a concave table of plaster of Paris, about three feet in diameter.