FOSTER (Samuel)

, an English mathematician, and astronomy professor of Gresham-college, was born in Northamptonshire, and admitted a Sizer at Emanuelcollege Cambridge in 1616. He took the degree of bachelor of arts in 1619, and of master in 1623. He applied early to the mathematics, and attained a great proficiency in it, of which he gave the first specimen in 1624, in a treatise on The Use of the Quadrant.

On the death of Mr. Gellibrand, he was chosen to succeed him, in 1636, as astronomy professor in Gresham-college, London. He quitted it again however the same year, though for what reason does not appear, and was succeeded by Mr. Mungo Murray, professor of philosophy at St. Andrews in Scotland. But this gentleman marrying, the professorship again became vacant, and Mr. Foster was re-elected in 1641.

Mr. Foster was one of those gentlemen who held private meetings for cultivating philosophy and useful | knowledge, which afterwards gave rise to the Royal Society. In 1646, Dr. Wallis, who was one of those associating gentlemen, received from Mr. Foster a theorem de triangulo sphærico, which he published in his Mechanics. Neither was it only in this branch of science that he excelled, but he was likewise well versed in the ancient languages; as appears from his revising and correcting the Lemmata of Archimedes, which had been translated into Latin from an Arabic manuscript by Mr. John Greaves. He made also several curious observations upon eclipses of the sun and moon, in various places; and was particularly noted for inventing, as well as improving, astronomical and other mathematical instruments. After a long declining state of health, he died at Gresham-college in 1652.

His printed works are as follow; of which the first two articles were published before his death, and the rest of them after it.

1. The Description and Use of a small Portable Quadrant, for the easy finding the hour of Azimuth; 4to, 1624. Originally published at the end of Gunter's Description of the Cross-Staffe, as an appendix to it.

2. The Art of Dialling; 4to, 1638. Reprinted, with additions, in 1675.

3. Posthuma Fosteri; by Wingate; 4to, 1652.

4. Four Treatises of Dialling; 4to, 1654.

5. Miscellanies, or Mathematical Lucubrations. Published by John Twysden, with additions of his own; and an appendix by Leybourne; folio, 1659.

6. The Sector altered, and other Scales added, &c. Published by Leybourne in 1661, in 4to.

There have been two other persons of the same name, who have published some mathematical pieces. The first was,

William FOSTER, who was a disciple of Mr. Oughtred, and afterward a teacher of the Mathematics in London. He distinguished himself by a book, which he dedicated to Sir Kenelm Digby, entitled, The Circles of Proportion, and the Horizontal Instrument, &c; 4to, 1633.—The other was

Mark FOSTER, who lived later in point of time than either of the other two, and published a treatise entitled, Arithmetical Trigonometry: being the solution of all the usual Cases in Plain Trigonometry by Common Arithmetic, without any tables whatsoever. 12mo, 1690.