Time and timekeepers / By Adam Thomson.

  • Thomson, Adam.
Date:
1842
Catalogue details

Licence: Public Domain Mark

Credit: Time and timekeepers / By Adam Thomson. Source: Wellcome Collection.

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    sent the stars in their relative positions, they drew these imaginary figures and placed the clusters of stars in different parts of them. These figures called constellations were formed for the purpose of finding a star with more facility by knowing in which part of the imaginary figure it was placed. It must have been soon observed that twelve of these constellations (the signs of the zodiac) became successively and periodically invisible, owing to the sun seeming to pass between them and the earth, and thus they were enabled to ascertain the duration of the solar year. The earth performs its revolution round the sun in 365 d., 5 h., 48 m., 49 s., 7 ten. No account was taken of the odd hours until the error in the computation of the year having become very con- siderable, Julius Caesar, with the assistance of Sosigenes, an Alexandrian astronomer, undertook, in the year b.c. 45, to reform the Calendar—to ac- complish which,the surplus 5h., 48 m., 49s., 7ten., were considered as six hours, making one day in four years; this day was, therefore, added to every fourth year by repeating the 24th of Febru- ary, which, according to the Roman method of computation, was the sixth day before the calends of March; hence the year in which this double sixth occurred was termed Bissextilis. To intro-
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