Pendulum measurements were made in the Strait of Magellan, at Punta Arenas. The sketch of Belgica Strait was drawn by taking, as principal points, twelve stations whose co-ordinates were astronomically determined. The other stations were obtained either by the method of sufficient segments or by that of magnetic bearings. We employed also Admiral Mouchez’s method. While drifting, the positions of the ship were observed and calculated either by Marcy Saint-Hilaire’s method or Borda’s, when the latitude had been determined beforehand by a culmination or a circummeridian. METEOROLOGY The only notions we had about the climate of the antarctic were based upon the very inadequate observations made during the three summer months. The Belgian Antarctic Expedition is the first which enables us to furnish a series of observations taken hourly during a full year. These observations were made during the year of the imprisonment of the _Belgica_ in the ice-pack between latitudes 70° and 71° 36′ south, and from longitude 85° to 103° west. In order to appreciate thoroughly the conclusions which can be derived from these observations, we must not forget that the _Belgica_, during her wintering in the ice-pack, was in the neighbourhood of free waters; in consequence, the climate studied is a coast climate, influenced partly by the neighbourhood of the sea, partly by that of the continental antarctic land mass covered with eternal snow. The definite corrections of figures obtained have not as yet been made; still, we are able to present the general results with an adequate approximation. The minimum temperature was observed in September; it was -43°. The maximum is remarkably low: +2° (in February). The month of July is the coldest of the year, with an average of -22.5°. The warmest month is February: average, -1°. The mean temperature of the year is -9.6°, an extraordinarily low figure for that latitude. North of the Spitsbergen, at latitude 80° north, we have -8.9°. The mean temperature in summer is -1.5°, a figure just as remarkable for its latitude, considering that the expedition of the _Fram_ obtained for a summer average -1.2° by latitude 84° north. This low temperature can only be explained by the absence of land towards the north, and the presence of an antarctic continent entirely covered with ice. This hypothesis is based upon a fact which was observed by the expedition. Every time the wind blew from the north the temperature rose, even in midwinter, to 0°, but did not ascend higher. As soon as the wind shifted and blew from the south the thermometer descended abruptly, even in the middle of summer, to a very low temperature.