The Rijksmuseum ait Leyden has several ‘pyrometers’, some with the recording
bar in-line with the specimen, as illustrated by Musschenbrock, and some with a
lever, as with the present instrument. Three of them were made by Jan Paauw Jnr
(c. 1723-1803), of Leyden, who is quite likely to have been responsible for the one
described here.
Musschenbroek (1731) XXX, fig. 1; repeated in Desaguliers (1734) XXIX, fig. 2;
M usschenbroek (1762) XXXIII, fig. 3; Ebeling (1789) 63; Crommelin (1951)1
20-21, 45-47; Chaldecott (1969), an important survey of metalline thermometers.
Inv 41I2
217 CONDUCTIVITY APPARATUS: Ingenhousz’ */4 igth C. (185) Fig. 192
Base area 155 x 100, height 100; length of inserted rods 150.
A rectangular copper box, with a hinged lid, has a black-painted wooden handle at
one side, and on the other is a row of six specimen rods. The rods are held by six
copper tubes that are set into the side of the box, and that extend half-way into it;
the inner ends of the tubes are sealed.
The rods are to be waxed and the box filled with hot water. The relative conductivity
of the heat along the rods is shown by the melting of the wax. The rods
are of: lead, glass, brass, zinc, iron, copper.
This piece of apparatus is named after Jan Ingenhousz (1730-1799) by Ganot,
Griffin, etc.
Ganot (1859) 235, fig. 142; Griffin (igio) 477.
218 CONDUCTIVITY APPARATUS: Rumford’s >/4 18th C. (1140) Fig. 193
Overall height 390, trough 302 x 100 x 100.
A tubular brass frame attached to a brass trough supports three thermometers that
dip into glass beakers. These beakers rest on brass shelves that have a hole cut in
them to let the hot water in the trough reach underneath the beakers. The mercury
thermometers have ivory scales marked from 0—80 by ones.
With different liquids in the beakers, the variation in conductivity can be
demonstrated. In the Inventory, this apparatus is attributed to “Thomson” ,
presumably Benjamin Thompson, Count Rumford. In one of his essays, Rumford
describes how he measured the heat flow through water, starch, and stewed apple.
Rumford (1798) Essay 7, “ Of the Propagation of heat in Fluids” .
Inv. 5114
219 Dr. CRAWFORD’S APPARATUS FOR SPECIFIC HEATS OF
GASES 1792 (210) Fig. 194
By Nairne & Blunt, London
Overall height 700, width 300; cylinder length 250, diameter 88.
Two brass cylinders with domed ends, presumably gilt lined inside (see below), are
attached to a supporting frame by brass tubes ending in turncocks. The cylindrical,
mahogany base piece can fit over a locating peg in a second part of the apparatus
now missing. The additional part consisted of two tinned vessels of twice the volume
of the brass cylinders, which held water and a pair of highly sensitive thermometers.
To position the cylinders accurately, the cross-bars on the frame have adjusting
screws.