Of Indo-China and Thibet the only information which reached Europe during the whole of the seventeenth century was due to the missionaries. Such names as Father Alexandre de Rhodes, Ant. d'Andrada, Avril, Benedict Goes, may not be passed over in silence. In their Annual Letters is to be found a quantity of information, which even in the present day retains a real interest, as concerning regions so long closed against Europeans. In Cochin China and Tonkin, Father Tachard devoted himself to astronomical observations, of which the result was to prove by the most conclusive evidence the great errors in the longitudes given by Ptolemy. This called the attention of the learned world to the necessity of a reform in the graphic representation of the countries of the extreme east, and for attaining this end, to the absolute need of close observations made by specially qualified scientific men, or by navigators familiar with astronomical calculations. The country which especially attracted the missionaries was China, that enormous and populous empire, which ever since the arrival of Europeans in India, had persevered with the greatest strictness in the absurd policy of abstention from any intercourse whatsoever with foreigners. It was not until the close of the sixteenth century that the missionaries obtained the permission, so often demanded before in vain, to penetrate into the Middle Empire. Their knowledge of mathematics and astronomy facilitated their settlement and enabled them to gather, as well from the ancient annals of the country, as during their journies, a prodigious quantity of most valuable information concerning the history, ethnography, and geography of the Celestial Empire. Fathers Mendoza, Ricci, Trigault, Visdelou, Lecomte, Verbiest, Navarrete, Schall, and Martini, deserve especial mention for having carried to China the arts and sciences of Europe, while they diffused in the west the first accurate and precise information upon the unprogressive civilization of the Flowery Land.