MARINE Chair, a machine invented by Mr Irwin, for viewing the satellites of Jupiter at sea, and of course determining the longitude by their eclipses. An account of it is given in the Journal Estranger for March 1760. An account of its accuracy was published the year following, by M. de L'Isle astronomer in the imperial academy of Petersburg: but notwithstanding the encomiums bestowed upon it by this gentleman, it hath never come into general use; and therefore we may conclude, that it is much inferior to the inventions of Mr Harrison for the same purpose. See HARRISON and NAVIGATION.