Volume 2

Outlines of natural philosophy : being heads of lectures delivered in the University of Edinburgh / by John Playfair.

  • Playfair, John, 1748-1819.
Date:
1814
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of natural philosophy : being heads of lectures delivered in the University of Edinburgh / by John Playfair. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    containing 998; of Maskelyne, containing only 36; but the places determined with such exactness, as to render it extremely valuable. See his Astro- nomical Observations, 1770. Bode's ^</as, Berlin, 1797, is the largest catalogue, . reduced into one body, that has appeared ; it con- tains 17,000. d. The number of the stars, however, visible with the telescope, far exceeds whatever can be reckon- ed. The bright tract in the heavens, called the Milky Way, seems to owe its white appearance to an incredible multitude of stars, which the eye can- not distinguish. Dr Herschel has seen 116,000 stars pass through the field of his telescope in a quarter of an hour; though the field was not more than 15' in diameter. 32. The most obvious distinction among the stars, is founded on their different magnitudes. Those of the first magnitude, are distinguished by particular names; there are only ten visible in Europe, which all astronomers have agreed to belong to that class. a. The stars visible to the naked eye, are divided, in all, into six classes, not very accurately separated from one another. The ancients counted 15 of the first, 45 of the second, 208 of the third. La Lande, § 557.