Micrographia - Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries Thereupon by Robert Hooke
page 105 of 465 (22%)
page 105 of 465 (22%)
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Cylindrical vessel stand, and as you perceive the ting'd liquor to rise in
both stems, with the point of a Diamond give several marks on the stem of the _Thermometer_ at those places, which by comparing the expansion in both Stems, are found to correspond to the divisions of the cylindrical vessel, and having by this means marked some few of these divisions on the Stem, it will be very easie by these to mark all the rest of the Stem, and accordingly to assign to every division a proper character. A _Thermometer_, thus marked and prepared, will be the fittest Instrument to make a Standard of heat and cold that can be imagined. For being sealed up, it is not at all subject to variation or wasting, nor is it liable to be changed by the varying pressure of the Air, which all other kind of _Thermometers_ that are open to the Air are liable to. But to proceed. This property of Expansion with Heat, and Contraction with Cold, is not peculiar to Liquors only, but to all kind of solid Bodies also, especially Metals, which will more manifestly appear by this Experiment. Take the Barrel of a Stopcock of Brass, and let the Key, which is well fitted to it, be riveted into it, so that it may slip, and be easily turned round, then heat this Cock in the fire, and you will find the Key so swollen, that you will not be able to turn it round in the Barrel; but if it be suffered to cool again, as soon as it is cold it will be as movable, and as easie to be turned as before. This Quality is also very observable in _Lead_, _Tin_, _Silver_, _Antimony_, _Pitch_, _Rosin_, _Bees-wax_, _Butter_, and the like; all which, if after they be melted you suffer gently to cool, you shall find the parts of the upper Surface to subside and fall inwards, losing that plumpness and smoothness it had whilst in fusion. The like I have also |
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