placed the loadstone mountains in Sarmatia. Mercator in his great chart depicted two great rocks rising from the sea to the north of eastern Siberia, one being drawn on the supposition that at St. Michael the compass points due north, while the other is further north on the supposition that the compass points due north at Corvo. The map of Cornelius Wytfliet, 1597, shows the same phantom islands. Blundevile, writing in 1594 of the now lost map of Peter Plancius, mentions that he sets down the pole of the loadstone somewhat to southward of the islands that lie east of Groynelande. Meantime another significant fact had been discovered in 1576 by Robert Norman, of Limehouse, compass-maker, namely, the tendency of the magnetized needle to dip its northern end downwards. Noticing this as a circumstance that occasioned him some trouble in the construction of his compasses, he thereupon devised a dipping-needle, and measured the dip, "which for this Cyty of London I finde by exact obseruations to be about 71 degrees 50 mynutes." He attributed both the declination and the dip of the needle to the existence of a "poynt respective," which the needle respected or indicated, but toward which it was not attracted. The first authoritative treatise on the variation of the compass was the tract by William Borough, comptroller to the Navy, who in 1580 found an eastward declination of 11° 15' at Limehouse. Borough had himself travelled in northern regions and had found at Vaigats a westerly declination of 7 degrees, whereas by Norman's theory of the respective point there should have been an easterly declination of 49° 22'. The great navigators were continually bringing home fresh information. Drake, Lynschoten, Cavendish, Hariot all contributed; as did lesser men such as Abraham Kendall, sailing-master to Sir Robert Dudley (the _soi-disant_ Duke of Northumberland), and afterward companion of Drake in his last voyage. Teachers of navigation such as Simon Stevin of Bruges and Edward Wright, lecturer to the East India Company, might record and tabulate: but a master-mind was wanting to forge some larger and consistent doctrine which should afford a grasp of the whole subject. Such an one arose in Dr. William Gilbert. Nurtured, as we have seen, in the Cambridge which had so recently been the home of Linacre and of Kaye--the Kaye who founded Caius College--Gilbert had, during his subsequent sojourn in Italy, conversed with all the learned men of his time. He had experimented on the magnet with Fra Paolo Sarpi: he had, there is reason to think, met Giordano Bruno: he was the friend and correspondent of Giovanni Francesco Sagredo. Being a man of means and a bachelor, he spent money freely upon books, maps, instruments, minerals, and magnets. For twenty years he experimented ceaselessly, and read, and wrote and speculated, and tested his speculations by new experiments. For eighteen years he kept beside him the manuscript of his treatise, which in the year