The British palladium; or, Annual miscellany: for the bissextile year 1768 : Containing annual and useful tables, and entertaining and interesting subjects in literature and science. With remarks on the nautical ephemeris, and the joint effect of refraction and parallax determined, for finding the longitude. Serving for land and sea. The twentieth number published. Humbly inscribed to the commissioners of longitude. By the author of The improv'd royal astronomer and navigator.