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A fine example of the watch form Avitreous Clinical Thermometer patented by Moritz Immisch in
England in 1882. The case is silver. These instruments are quite small and finely made with jeweled movement: the face is about the
size of a US quarter dollar coin. The thermometer dial is calibrated in degrees Celcius from 21 to 45 and the face is embossed with "Autothermographe"
in script, and some decorative scrollwork below. A serial number (18124) is printed at the bottom of the dial.
Included is the original separate protective outer case in nickel plate. The instrument is in very fine condition without dings or
significant scratches to either the silver case or glass, and the thermometer still functions and responds appropriately to
temperature changes. The outer case is also in fine condition, noting only a slightly wobbly hinge and a couple of very small plating
blemishes. It holds a protective red velvet disk which is probably not original.
The mechanism uses a volute tube filled with a highly expansive fluid (e.g., ether or alcohol). Acting on the Bourdon principle,
temperature changes cause the tube to expand or contract. With one end of the tube fixed, the resulting motion of the other end is
transferred to the pointer which is connected to the movable end of the volute via fine rack and pinion.
These were advertised as "Easy to read and easy to use, but not easy to break. Will
never vary with age, like the glass thermometer." Although they were each calibrated by the Kew Observatory and bore certificates of
accuracy from that institution, they never really caught on, and became obsolete by the early 1900's.
Click this link for a copy
of the patent.
ca 1890
$720
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