The degrees of least curvature will be longest, and those of greatest curvature shortest; that is, one would have to travel farther on the flattened part of the earth to see any difference in the position of the north-star than in those parts where the curvature is greater. So a degree of latitude near the pole, if determined by the position of the north-star, would be found, by actual measurement, to be longer than one similarly determined at the equator. It was to ascertain whether the fact was so that the two scientific expeditions were sent out. The party which was sent to the northern regions travelled over snow and ice, swamps and morasses, to the arctic circle, and fixed their station at Tornea, in Lapland. The frozen surface of the river afforded them a convenient level for fixing what is called by surveyors the base line. The cold was so intense, that the glass froze to the mouth when they drank, and the metallic measuring rod to the hand. In spite, however, of perils and discomforts, they persevered in their task, and brought back careful measurements of a degree in latitude 66° north, to be compared with those made by the other party at the equator, whose movements we propose more particularly to follow. Before we take leave of the northern commissioners, however, we will mention another method they took of demonstrating the same fact. If the earth be depressed at the poles, it must follow that bodies will weigh heavier there, because they are nearer the centre of the earth. But how could they test this fact, when all weights would be increased alike,--the pound of feathers and the pound of lead? The question was settled by observing the oscillation of a pendulum. The observers near the pole found that the pendulum vibrated faster than usual, because, being nearer the centre of the earth, the attracting power was increased. To balance this, they had to lengthen the pendulum; and the extent to which they had to do this measured the difference between the earth's diameter at the poles, and that in the latitude from which they came.