3. “Mercator’s Chart.” In all the charts in use before Mercator’s, curved lines were drawn representing the meridians and parallels. A vessel which followed these lines always receded too far from the equator, and, if land did not intervene, would describe a spiral course and finally reach the pole. Mercator constructed a map as follows: A line, AB, was drawn representing the equator, and was divided into 36, 24 or 18 equal parts for meridians at 10°, 15°, or 20° apart, and the meridians were then drawn through them perpendicular to AB. The distance of the parallels and the tropics, and the arctic circles were marked from the equator on the sides, and these points joined by straight lines. The map does not give a natural representation, as the polar regions are immensely exaggerated. The distortions in the form of the countries and the relative distances of places are rectified by making the degrees of latitude increase proportionably to those of longitude. 4. “Quadrant.” Quadrants were used for surveying, making astronomical observations, and, in navigation, for determining the meridian altitude of the sun, and from that the latitude of the observer. They were made of a great variety of form and size to suit their several uses. The interest attaching to them at the present time is chiefly historical, as they have been superseded by the sextant and the full circle. “Davis.” An eminent English navigator of the latter part of the sixteenth century. “Hadley,” John. An English mathematician of the early part of the eighteenth century. An intimate friend of Newton. TALK ABOUT BOOKS. That most remarkable poem of the Orient, the “Rubáiyát”[J] of Omar Khayyám, has recently had the rare fortune of receiving from translator, artist and publisher an almost perfect treatment. Its translation places it among English classic poems, its illustration and make-up among American classic art books. This poem, very imperfectly known among us, is the work of a Persian astronomer and poet, Omar Khayyám, or Omar the Tent-Maker, a native of Naishapúr, in Khorassan. He was born in the latter half of the eleventh century, and became a favorite of the rulers of the realm. His life was, so goes the chronicle, “busied in winning knowledge of every kind, and especially in astronomy, wherein he attained to a very high preēminence. Under the Sultanate of Malik Shah, he came to Merv and obtained great praise for his proficiency in science, and the Sultan showered favors upon him.” Omar was an honest thinker; he refused the hollow mysticism of the times, and framed a system which approaches Epicureanism. His views of life, his fruitless search for Providence, his sad conclusion, “I came like water, and like wind I go,” together with his final refuge in the wine cup, with the command “Drink, for you know not whence you came nor why, Drink, for you know not why you go, nor where,”