200 ENGLAND'S ATTEMPTS TO KEACH INDIA the thanks of the Republic to Prince Pedro of Portugal for his good offices in negotiating a treaty with the emperor. This doctrine du secret commercial, which weighed heavily on early exploration, ceased to be tenable in the sixteenth century. Prince Henry's cartographical school at Sagres, in the fifteenth, had done much to render available the then existing stock of knowledge regarding the undiscovered world. But it was the ap- plication of the Flemish printer's and graver's art to map-making at the beginning of the sixteenth century that gave the death-blow to secret commerce. A mag- nificent school of cartography grew up at Antwerp and Bruges a school ennobled by master-minds like Mer- cator, Ortelius, and De Jode, and fertile in processes of map-reproduction destined to make the discoveries of one nation the common property of all. The Netherlands school of geographers rendered possible the developments in maritime commerce which culminated at the end of the sixteenth century in the English and Dutch East India Companies. It started from the theoretical cosmography of the Ptolemaic sys- tem, and the Roman itineraries of which the Peutin- gerian Tables (circ. 226 A. D.) form a striking example. To these it added the actual discoveries, and some of the conjectural errors, embodied in the mappemondes and portulans of the middle ages. The voyages of Columbus and Da Gama made the mediaeval charts obsolete. On the ruins of the old cosmography the Italian and Dutch map-designers built up a new geog-
