A popular writer on astronomy and mechanics, born at Rothiemay, Banff, son of a laborer; his interest in astronomy was first aroused by his observation of the stars while acting as a "herd laddie," and much of his time among the hills was spent in the construction of mechanical contrivances; compelled by circumstances to betake himself to various occupations, pattern-drawing, clock-mending, copying prints, and portrait sketching, he still in his leisure hours pursued those early studies, and coming to London in 1743 (after a residence of some years in Edinburgh), began lecturing on his favourite subjects; a pension of £50 was granted him out of the privy purse, and in 1763 he was elected an F.R.S.; besides publishing lectures on mechanics, hydrostatics, optics, etc., he wrote several works on astronomy, chiefly popular expositions of the methods and principles of Sir Isaac Newton (1710-1776).