Varieties Of Thermometers

Fig. 37 is an illustration of boxwood scale thermometers for general use and common purposes.

Fig. 38, Negretti and Zambra’s Travelling Thermometer; it is fixed in a plated metal (silver or otherwise) case, similar to a pencil-case, and has the scale divided upon its stem.

Fig. 39, Thermometer mounted on a slab of glass, upon which the scale is etched, the back being either oak, mahogany, or ebony.

Fig. 40, Portable Thermom

ter, in a bronzed brass or German silver revolving case.

Fig. 41, Pocket Thermometer, on ivory or metallic scale, in morocco or papier-mâché case.

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Fig. 42, an Ornamental Drawing-room Thermometer, on ebony or ivory stand, with glass shade.

Fig. 43, representation of highly carved or engine-turned design for thermometer mounts, in ivory or wood, for the drawing-room. Some have the addition of a sundial or compass at the top; they may also be formed for a watch-stand.

Fig. 44, Bath Thermometer, having a float to admit of its being kept in the water.

Fig. 42.	Â	Fig. 43.	Â	Fig. 44.	Â
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Fig. 45, Thermometer with ivory scale in glass cylinder, mounted on oak bracket with metal top, for out-door use; as at a window.

Fig. 46, Thermometer for the window, on patent porcelain or glass scale, with oak bracket and convenient brass supports, for placing the instrument at any angle.

Fig. 47, Chemical Thermometer, on boxwood scale, jointed near the bulb on a brass hinge, ranging from 300° to 600°.

Fig. 48, Chemical Thermometer, for acids, graduated on its own stem, suitable for insertion in the tubulure of retorts; they are also made insulated in glass cylinder to protect the graduated stem; ranging from 0° to 600°.

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Superheated Steam Thermometer.—The great advantage gained by the use of superheated steam in marine and other steam-engines being now generally admitted by engineers, reliable thermometers, reading to 600° at least, are of the utmost importance. To meet this want, Messrs. Negretti and Zambra have constructed for the purpose a substantial form of thermometer, on their patent porcelain scales, in strong and convenient metal mountings, with perforated protection to the bulb. The scales cannot be deteriorated by steam, heat, oil, or dirt; and an occasional wiping will be all that is necessary to keep the divisions and figures clean and visible for any length of time; while careful calibration of the thermometer tubes ensures the most accurate indications attainable. These thermometers are illustrated by figs. 49 & 50. A similar, but cheaper, construction is given to thermometers to be used with hot air, or hot water, apparatus.

Thermometer for Sugar Boiling is protected by a metallic frame; and is usually from three to four feet long, the graduations being confined to a space of about twelve inches at the upper part of the instrument, allowing the bulb and greater part of the tube to be immersed in the boiling sugar. The graduations extend to 270° or further. An index is sometimes attached to the scale, which may be set to any degree of heat required to be maintained.