Rare Immisch Avitreous Skin Thermometer No 1996 C1881

A very rare antique silver Immisch patent volute tube or avitreous skin thermometer no 1196 retailed by Krohne & Sesemann, London c1881. Immisch thermometer with 1″ silvered and hand decorated guilloche dial having dual concentric temperature scales, the outer calibrated in degrees Fahrenheit with a range from 45 – 115 and body temperature of 98.4 degrees indicated by an arrow, the inner marked with degrees Celsius having a range from 7 – 46, set on a circular linear register marked “Patent” to the lower part with the retailer’s details, “Krohne & Sesemann, Patent, London.” The centre with engine turned pattern, the lower part serial no. “1196.” Fine blued steel pointer, low dome bevelled crystal. The miniaturised jewelled movement based on a fluid, probably alcohol, filled Bourdon tube, constructed principally in brass, tensioned on a blued steel hair spring with amplification by levers and mounted between two plates, rack and pinion transmission to pointer. All contained within a silver case, with case extension and suspension ring. Together with its original oxblood moroccan leather over timber, light and dark blue silk and velvet lined presentation case, gilt brass swinging catch and keeper. Condition: Overall very crisp, the dial clean and vibrant, the silver case essentially dent free, some minor marks and oxidation. The mechanism working well with near instant deflection at temperature increase. The presentation case sound, the external leather in good condition, the fabric lining generally good, some discolouration to lid silk. Comments: Very rare and of great interest, especially to collectors in medical science, this is one of those instruments that is wonderful both outwardly as well as inwardly, the case, movement and dial maker’s skill very evident. The British patent was granted to Karl Moritz Immisch in July 1881 and was generally received with great acclaim. The term "avitreous" was applied to it by George Matthews Whipple, Superintendent of the Kew Observatory, who commented in a letter to Nature journal, published 15 July 1886: "In your article, p. 234, referring to this pretty little instrument, you refer to the appellation “metallic” as not a happy one in describing it. This I pointed out to the maker some time ago, and termed it an avitreous thermometer, as glass plays no part in its construction beyond that of a protector to the dial. The certificates of verification are printed with the instrument so designated, and probably the erroneous term will soon drop out of use." This system, based upon a Bourdon tube applied to temperature measurement, was considered the finest of its mechanical type in its time, received many awards, and has stood the test of time. Held in the hand – or more correctly, held to the wrist – it almost immediately responds, showing very good sensitivity. It appears to be relatively accurate as well. Mechanical thermometers manufactured in the 19th century are rare, predominantly as they were substantially more expensive than the simple mercurial thermometer. There was also some general reluctance to accept that they could be as accurate. This Immisch skin thermometer is a very unusual and delightfully appealing piece of great rarity and undeniable quality, clearly by one of the world’s pre-eminent instrument makers.