Treatise on heat / By the Rev. Dionysius Lardner.

  • Dionysius Lardner
Date:
1833
Catalogue details

Licence: Public Domain Mark

Credit: Treatise on heat / By the Rev. Dionysius Lardner. Source: Wellcome Collection.

    16/446 page 4
    it. Such distortion, and the variations to which it is subject, must then be accurately ascertained, before any inference can be made respecting the motion, position, magnitude, or distance of any object in the heavens; and ascertained it cannot be unless the laws wliich govern tlie phenomena of lieat be known. But the very instruments wliich the same astro- nomer uses to assist liis vision, and to note and measure tlie positions and mutual distances of the objects of his enquiry, are themselves eminently sub- ject to the same distorting influence. The metal of which tliey arc formed swells and contracts with every fluctuation in the heat to which it is exposed. A sunbeam, a blast of cold air, nay, the very heat of the astronomer’s own body, must [iroduce effects Tin the figure of the brazen arch by whose divided surface his measurements and his observations are effected. Such effects must therefore he known, and taken into account, ere he can hope to attain that accuracy which the delicacy of his investigations renders indispensably necessarj^ The chemist, in all his proceedings, is beset with the effects of heat aiding or impeding his researches. Now it promotes the disunion of combined ele- ments; now fuses into one uniform mass the most heterogeneous materials. At one time he resorts to it as the means of arousing dormant affinities — .at another he apjilies its powers to dissolve the strongest bonds of chemical attraction. Compo- sition and decomposition are equally attended by its evolution and absorption; and often to such an extent as to produce tremendous exiilosions on the
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