File:Chambers's encyclopedia; a dictionary of universal knowledge for the people (1871) (14766275102).jpg

Identifier: chamberssencyclo07phil (find matches)
Title: Chambers's encyclopedia; a dictionary of universal knowledge for the people
Year: 1871 (1870s)
Authors:
Subjects: Encyclopedias and dictionaries
Publisher: Philadelphia : J. B. Lippincott & Company Edinburgh, W. & R. Chambers
Contributing Library: University of California Libraries
Digitizing Sponsor: Internet Archive

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^.jaw^ Vo). VII., pn-e375. PENELOPE—PEXGUIN. seconds peudiilum in any locality. The simple pen-dulum is perfect in theory, but cannot be con-Btructed ; and thus the method which enables us toobtain its results by the help of such a pendulum aswe can construct, is especially valuable. Compensation Penduluvi.-—As the length of a rodor bar of any material depends on its temperature(see Heat), a clock with an ordinary pt-udulumgoes faster in cold, and slower in hot, weather.Various contrivances have been devised for thepurpose of diminishing, if not destroying, theseeffects. The most perfect in theory, though per-haps not the most available in practice, is thatof Sir D. Brewster (q. v.), founded upon the experi-mental discovery of Mitscherlich, that some crjstalsexpand by heat in one direction, while contractingui the perpendicular one ; and therefore that arod may be cut out of the crystal in such a direc-tion as not to alter in length by any change oftemperature. In the method of co

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