at South Kensington . 
379 
1876.] 
Observatory, in 1843, by Ronalds, for the purpose of ob- 
serving atmospheric electricity, consisting of a principal 
conductor, with its glass support, umbrella, and heating 
apparatus; its voltaic collecting lantern; Volta’s electro- 
meters and sights ; a Henley electrometer ; a Gourgon gal- 
vanometer; a discharger, or spark measurer; and a Bennet’s 
gold-leaf electroscope. 
Early rheostat, given by Faraday to Sir Charles Wheat- 
stone. 
The original Wheatstone’s bridge. 
Cooke and Wheatstone’s earliest needle instrument, 1837. 
— The letters are indicated by the convergence of two 
needles. The five line-wires required for the instrument 
were inserted in grooves in a triangular piece of wood, and 
wire laid underground. 
Original five-needle telegraph dial. — (Wheatstone Collec- 
tion of Physical Apparatus, King’s College, London.) 
Three ABC telegraph-sending instruments, showing gra- 
dual improvements. 
First eleCtric key, constructed by Sir Charles Wheatstone. 
Wheatstone’s first relay instrument. 
Two early forms of stereoscope. — (Wheatstone Collection 
of Physical Apparatus, King’s College, London.) 
Jewel lens (ruby) of i-6oth inch focus. — Produced by 
Mr. Andrew Pritchard, at the suggestion of Sir David 
Brewster. 
Brewster’s patent kaleidoscope (with case). — The original 
form of the instrument made by Bate, of London, in the 
year r8i5. 
Otto von Guericke’s original air-pump. 
Air-pump with two barrels. — The first pump of the kind 
ever constructed. It is an exhausting and a condensing 
pump, and was made for King George III. in 1761. 
Original spirit thermometer, of the Florentine Accademia 
del Cimento (17th century). — Presented to the Royal Insti- 
tution by Sir Henry Holland, Bart., F.R.S. 
Wedgwood’s pyrometer, invented in 1782. — Dry clay 
when exposed to high temperatures contracts uniformly, 
and Wedgwood believed that by the amount of contraction 
the temperature which produced it could be measured. The 
instrument, however, is not reliable. This specimen was 
made by Josiah Wedgwood, and presented to the Edinburgh 
Museum by his grandson, Mr. Godfrey Wedgwood. 
Daniell’s pyrometer, employed in researches by Professor 
DanielL 
