Annals of Philosophy Volume 23 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1824 Excerpt: ... Dulong and Petit particularly mention, that they found all the varieties of glass which they used, to have the same expansive power; this appears surprising, for I can truly afhrm, that every specimen of crystal differs more or less from another; trials by mercury give from to as the fractions expelled, in the range from freezing, to boiling water, even while the mercury has undergone the same rigorous and repeated boilings, these fractions indicating elongations of glass rods, by that increase of temperature, from-r. to That crystal which is the most colourless is commonly the most ductile and least expansible; but neither from its specific gravity, nor from its tint, as seen through the axis of a tube, can we estimate its expansive power; besides, it is commonly known that tubes of every description, in course of time, become less ductile; hence it is not improbable, that a change takes place in their rates of expansion. Having been at first induced by the highly sanctioned celebrity of the Memoir to peruse it with a view to establish a froper graduation of the higher part of the thermometric scale, may, on some future occasion, show, what that graduation ought to be, for the degrees above 212, and for those below 32; beyond which two unalterable points, no scale hitherto laid down, gives indications corresponding to those of the degrees within the limits of the primary thermic unit. Besides, as it must be granted that an error exists in the lower part of the mercurial thermometer, so must it likewise in that filled with spirit of wine, and probably to a greater extent; as perhaps it has never been proved, that the expansive powers of alcohol are, for equal increments of heat, similar to those of mercury, particularly at the low temperatures reported by ...