Chap. LXXIV.—Of a Figure moving against the Wind, Plate VIII.
A man moving against the wind in any direction does not keep his centre of gravity duly disposed upon the centre of support[18].
Chap. LXXV.—Of the Balance of a Figure resting upon its Feet.
The man who rests upon his feet, either bears the weight of his body upon them equally, or unequally. If equally, it will be with some accidental weight, or simply with his own; if it be with an additional weight, the opposite extremities of his members will not be equally distant from the perpendicular of his feet. But if he simply carries his own weight, the opposite extremities will be equally distant from the perpendicular of his feet: and on this subject of gravity I shall write a separate book[19].
Chap. LXXVI.—A Precept.
The navel is always in the central or middle line of the body, which passes through the pit of the stomach to that of the neck, and must have as much weight, either accidental or natural, on one side of the human figure as on the other. This is demonstrated by extending the arm, the wrist of which performs the office of a weight at the end of a steelyard; and will require some weight to be thrown on the other side of the navel, to counterbalance that of the wrist. It is on that account that the heel is often raised.
Chap. LXXVII.—Of a Man standing, but resting more upon one Foot than the other.
After a man, by standing long, has tired the leg upon which he rests, he sends part of his weight upon the other leg. But this kind of posture is to be employed only for old age, infancy, or extreme lassitude, because it expresses weariness, or very little power in the limbs. For that reason, a young man, strong and healthy, will always rest upon one of his legs, and if he removes a little of his weight upon the other, it is only a necessary preparative to motion, without which it is impossible to move; as we have proved before, that motion proceeds from inequality[20].
Chap. LXXVIII.—Of the Balance of Figures, Plate IX.
If the figure rests upon one foot, the shoulder on that side will always be lower than the other; and the pit of the neck will fall perpendicularly over the middle of that leg which supports the body. The same will happen in whatever other view we see that figure, when it has not the arm much extended, nor any weight on its back, in its hand, or on its shoulder, and when it does not, either behind or before, throw out that leg which does not support the body.