|
Of THEODOSIUS himself nothing is known. One Theodosius of Bithynia is cited as a mathematician by Vitruvius as the inventor of a universal sun-dial. A Theodosius of Tripolis is cited by Pappus and others, and was said to be later than the reign of Trajan, in the second century A.D. Some authorities have attributed the extant works to the latter. But perhaps the Theodosius of Bithynia was subsequently settled at Tripolis, and is the same who is mentioned by Pappus. He has left three works--on Spherical Geometry, on Habitations (a work on astronomical geography), and on Days and Nights.
In the first are stated and proved several important propositions, as that the section of a sphere by a plane is a circle; that the plane touches the sphere in one point only, the line from which to the centre is perpendicular to the plane; that every circle passing through the centre is a great circle; that secondary circles parallel to a great circle, and at equal distance, are equal to each other; that great circles mutually bisect; that the distance of the pole of a great circle to any point of its circumference is the side of the inscribed square.
The treatise on Habitations describes the different aspects of the heavens visible at different parts of the earth's surface, according to their latitude and longitude.
The third treatise, on Days and Nights, is an attempt to fix the precise variation of the day and night throughout the sun's annual path through the heavens, and to determine the period within which these variations will occur in the same way; in other words, to fix the precise relations of the day and the year.
| This biography is
reprinted from The New Calendar of Great Men. Ed. Frederic
Harrison. London: Macmillan and Co., 1920. |
|
