Description of an apparatus for maintaining a constant temperature under the microscope / by E.A. Schäfer.

  • Sharpey-Schäfer, E. A. (Edward Albert), Sir, 1850-1935.
Date:
[between 1880 and 1889?]
Catalogue details

Licence: Public Domain Mark

Credit: Description of an apparatus for maintaining a constant temperature under the microscope / by E.A. Schäfer. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    with the outlet. The reservoir surrounds the bulb of a mercurial gas regulator (fig. 2, d; and fig. 3), and is heated below by a minute gas flame; it will be readily understood that the heated water in the reservoir must rise up through the inflow tube into the stage, while the colder fluid passes into the reservoir through the lower tube to supply its place. The chamber in the centre of the stage is, when in use, closed below by a circular cover-glass, which is placed on a rim made for its reception, and previously oiled; above, it is covered by the cover-glass, on which the object is placed; it communicates, however, with the exterior by means of a small lateral tube which passes through the body of the stage, but is entirely shut off from the surrounding fluid. The bulb of a small thermometer may be introduced through this lateral tube whenever it is wished to ascertain the tem- perature of the central chamber (see fig. 1, c, in horizontal section). This method of measuring the temperature has a considerable advantage over that in which the thermometer- bulb encircles the wall of the chamber and lies in the surrounding fluid, for this last is always very perceptibly warmer than the interior of the chamber. It has the dis- advantage that observations cannot be made while the ther- mometer is in situ, but this can be met by slightly withdrawing the instrument into the lateral tube. Indeed, ordinarily it will be sufficient, when the desired temperature is attained and the regulator set, to remove the thermometer altogether ; the lateral tube may then serve, if necessary, for the intro- duction of a small tube conducting gas or vapour to the specimen under observation. The gas regulator may be described as a mercurial thermo- meter with its tube open above, and with two side tubes leading from it, one near the bulb, the other near the top (fig. 3). To the lower side tube is cemented a steel collar ([h), in which a screw of the same metal accurately fits ; by working this screw the mercury may be raised or lowered in the thermometer tube. A fine steel tube (/), with a slit at its lower end, passes down a certain way into the thermometer, being cemented around its upper orifice. The gas is made to pass down this fine steel tube, and then up between it and the walls of the thermometer tube; finally, it is conducted out by the upper side tube, and by means of india-rubber tubing to the burner below (as indicated by the arrows in figs. 2 and 3). To “ set ” the regulator, when the central chamber of the stage has attained the desired temperature, all that is necessary is to turn the steel screw until the mercury is forced up to the slit in the steel tube; the gas is now cut off.