Referring to the last table, it will be seen that the two stakes numbered 12 and 13 moved with a common velocity of 23-1/4 inches per day, and that their motion is swifter than that of any of the others. The point of swiftest motion may be taken midway between them, and this point was found by measurement to lie 233 yards _west_ of the dirt which marked the junction of the Glacier du Geant with its fellow tributaries: whereas, in the former cases, it lay a considerable distance _east_ of this limit. Its distance from the eastern side of the glacier was 601 yards, and from the western side 262 yards, being 170 yards west of the centre of the glacier. [Sidenote: CONJECTURE TESTED.] But the measurements enabled me to take the stakes in pairs, and to compare the velocity of a number of them which stood at certain distances from the eastern side of the valley, with an equal number which stood at the same distances from the western side. By thus arranging the points two by two, I was able to compare the motion of the entire body of the ice at the one side of the central line with that of the ice at the other side. Stake 17 stood about as far from the western side of the glacier as stake 3 did from its eastern side; 16 occupied the same relation to 4; 15, to 5; 13, to 7; and 12, to 9. Calling each pair of points which thus stand at equal distances from the opposite sides _corresponding points_, the following little table exhibits their comparative motions:-- Numbers and Velocities of Corresponding Points on the Fourth Line. No. Vel. No. Vel. No. Vel. No. Vel. No. Vel. West 17 15 16 17-1/4 15 22-1/4 13 23-1/4 12 23-1/4 East 3 12-1/2 4 15-1/4 5 15-1/2 7 18-1/4 9 19-1/2 [Sidenote: WESTERN HALF MOVES QUICKEST.] The table explains itself. We see that while stake 17, which stands _west_ of the centre, moves 15 inches, stake 3, which stands an equal distance _east_ of the centre, moves only 12-1/2 inches. Comparing every pair of the other points, we find the same to hold good; the western stake moves in each case faster than the corresponding eastern one. Hence, _the entire western half of the Mer de Glace, at the place crossed by our fourth line, moves more quickly than the eastern half of the glacier_. We next proceeded farther up, and tested the contrary curvature of the glacier, opposite to Trelaporte. The station chosen for this purpose was on a grassy platform of the promontory, whence, on the 28th of July, a row of stakes was fixed at right angles to the axis of the glacier. Their motions, measured on the 31st, gave the following results:-- Fifth Line.[B]--Daily Motion.