him by his friend Edward Vright, and an explanation of principle of Mercator's projectiou. Hondi,s, in 1595, published at Amsterdam a new chart of the world on Mercator's projection, in the prcparatiou of which he utilised XVrigh's tdles. Blagrave and Hood improved the astrolabe and cross-staff. I ]{ues expounded various problems in navigati.n, and included in his 'Tracttus de Globis' ), a chapter by Herlot on the use of rhumhs. John Dt[vis, the navigator, wrote 'The Sealnan's Secrets' in 1594, and invented the hack-staff or, ])avis's quadrant, which rapidly super-

(Frm John .bert,m's ' Eb'mtls qf 5trigation.' Lombre, 1742.) sealed the cross-staff, and which, improved by Fl;;msteed, remai.ed in common use nntil Hadley's reflecting quadrant took its place in 1731. And Doctor Gilbert of Colchester, in the last year of the century, followed up the previous works by orough, Norlnan, and othe, on magnetism, by propounding the theory that the earth itself is a magnet. Nor must the invention of the telescope be forgottcn. It is due to Zachari;ts J;mssen, of Middclherg, about 1590, and the instrtent, quickly improved, soon became part of the se; captain's equipment.

Henry VII., unlike some of his fifteenth-century predeccssors,