This was how Dr. Knight made the bars of the two great magnets of the Royal Society. Each magnet contained two hundred and forty bars, fifteen inches long, one inch wide and half an inch thick. Dr. Robison described, in 1800, the effect of pressing together the dissimilar poles of the two magnets, and, thirty years later, Prof. Faraday, upon placing a soft iron cylinder, one foot long and three-quarters of an inch in diameter, across the dissimilar poles, found that he required a force of one hundred pounds to break down the attractive power. Previously to Dr. Knight’s discovery, the method of making artificial magnets most in use was by simply rubbing the bar to be magnetized upon one of the poles of a natural magnet in a plane at right angles to the line joining its two poles. Another secret of Dr. Knight was also, after his death, made known to the Royal Society by its secretary, Mr. Benjamin Wilson. It was the mode of making artificial paste magnets. He collected a large quantity of iron filings, which he cleansed and made into a fine powder under water and afterward dried and mixed, preferably with linseed oil. This was baked into cakes, which were magnetized by placing them between the ends of his magazine of artificial magnets. To Dr. Knight was given the first English patent in the Class of Electricity and Magnetism. It bears date June 10, 1766, No. 850, and is for the construction of “Compasses so as to prevent them being affected by the motion of the ship,” etc. REFERENCES.--_Phil. Trans._, Vol. XLIII. pp. 161, 361; Vol. XLIV. p. 656; Vol. XLIX. p. 51; Vol. LXVI. p. 591; C. R. Weld, “Hist. of Roy. Soc.,” Vol. I. p. 511; Noad, “Manual,” 1859, p. 593; Sturgeon, “Sc. Researches,” Bury, 1850, p. 249; also the abridgments by Hutton, Vol. IX. pp. 71, 74, 122, 390 (Folkes), 653; Vol. X. pp. 64, 67; Vol. XIV. pp. 117, 480; and by John Martyn, Vol. X. part ii. pp. 678–698. =A.D. 1746.=--Gravesande (Wilhelm Jacob), celebrated Dutch mathematician and natural philosopher (1688–1742), whose family name was Storen Van ’Sgravesande, is the author of “Eléments de physique démontrés mathématiquement ... ou introduction à la philosophie Newtonienne,” which was translated from the Latin and published at Leyden in 1746. At p. 87 of the second volume of the last-named work he gives a description of an electrical machine constructed on the plan of that of Hauksbee. It consisted merely of a crystal globe, which was mounted upon a copper stand, and against which was pressed the hand of the operator while it was made to revolve rapidly by means of a large wheel.