Thomas Godfrey, an American mathematician, born in Philadelphia, died in December, 1749. He had but a common education, and followed the business of a glazier in his native city; but he mastered all the books on mathematics that he could obtain, and learned Latin to read mathematical works in that language, He borrowed a copy of Newton's Principia from James Logan, secretary of the commonwealth, and in 1730 communicated to him an improvement that he had made in Davis's quadrant. In 1732 Logan gave an account of the invention to Edmund Halley of England, and Godfrey also prepared a description of it addressed to the royal society of London, but did not send it, awaiting the effect of the letter to Halley. No answer was received after an interval of a year and a half, and then the invention of Godfrey was laid before the royal society by the botanist Peter Collinson. Mean-time, in 1731, Mr. Halley had presented a paper containing a full description of an improvement of the quadrant similar to that of Godfrey. The rival claims were investigated by the royal society, and it was decided that they were both entitled to the honor of the invention, and a reward of £200 was bestowed on Godfrey, in household furniture instead of money, on account of his intemperate habits.

Godfrey's or Halley's quadrant is the same in principle and application as the sextant.