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The Edinburgh philosophical journal (1821)
The Edinburgh philosophical journal - 1821 Author:David Brewster Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: The bellmen are in general very stout and healthy: their hard labour requires very good sustenance of three substantial meals in the day. Tea, bread, butter, egg... more »s, bacon, potatoes, and fish, are their common diet. They are not particularly addicted to spirituous liquors. A little is very necessary for them, and it would require a good deal to aflect them much. I cannot conclude this paper, without repeating my best thanks to Mr Bald and Mr Souter, to whose kindness and liberality I am indebted for the greater part of the details intror duced into this paper. Edinburgh, April l821. Art. III. — Remarks on a Passage in the Mathematical Collections of Pappus, from which the Obliquity of the Ecliptic has been deduced. S, who was born 276 years before Christ, determined, by his own observations, that the obliquity of the ecliptic was 23 51' 19"5. This quantity was adopted by Hipparchus, who lived about 100 years later, and even Ptolemy may be said to ha%re used the same. M. Delambre -f-, indeed, seems to think, that Ptolemy did not observe much himself; but, although he lived about 400 years later than Eratosthenes, even this interval would only have diminished the angle by a very few minutes, which probably was too small a quantity to have been ascertained by the instruments then iIi use. These records, however, of ancient astronomy, have always been considered as very important for ascertaining the variation of the angle, which the equator makes with the ecliptic ; but there is. another, which gives a result wholly irreconcileable with them. This is found in Pappus's Mathematical Collections, Book vi. Theor. 35., and the obliquity derived from the data there detailed, is no more than 23 2y 55". Now, Pappus lived, according to Suidas, under the elder Theodosius, and consequ...« less