XXXVII. Account of an extraordinary Shower of black Dust, that fell in the Island of Zetland 20th October 1755[194]. In a Letter from Sir Andrew Mitchell, of Westshore, Bart. to John Pringle, M.D. F.R.S. · Philosophical transactions, Vol. L. Part I. For the year 1757. / Giving some account of the present undertakings, studies, and labours, of the ingenious, in many considerable parts of the world.