20. To what has been said of motion, I will add what I have to say concerning habit. Habit, therefore, is a generation of motion, not of motion simply, but an easy conducting of the moved body in a certain and designed way. And seeing it is attained by the weakening of such endeavours as divert its motion, therefore such endeavours are to be weakened by little and little. But this cannot be done but by the long continuance of action, or by actions often repeated; and therefore custom begets that facility, which is commonly and rightly called habit; and it may be defined thus: HABIT is motion made more easy and ready by custom; that is to say, by perpetual endeavour, or by iterated endeavours in a way differing from that in which the motion proceeded from the beginning, and opposing such endeavours as resist. And to make this more perspicuous by example, we may observe, that when one that has no skill in music first puts his hand to an instrument, he cannot after the first stroke carry his hand to the place where he would make the second stroke, without taking it back by a new endeavour, and, as it were beginning again, pass from the first to the second. Nor will he be able to go on to the third place without another new endeavour; but he will be forced to draw back his hand again, and so successively, by renewing his endeavour at every stroke; till at the last, by doing this often, and by compounding many interrupted motions or endeavours into one equal endeavour, he be able to make his hand go readily on from stroke to stroke in that order and way which was at the first designed. Nor are habits to be observed in living creatures only, but also in bodies inanimate. For we find that when the lath of a cross-bow is strongly bent, and would if the impediment were removed return again with great force; if it remain a long time bent, it will get such a habit, that when it is loosed and left to its own freedom, it will not only not restore itself, but will require as much force for the bringing of it back to its first posture, as it did for the bending of it at the first.
Vol. 1. Lat. & Eng.
C. XXII.
Fig. 1-3
| [Fig 1.] | [Fig 2.] | [Fig 3.] |
CHAP. XXIII.
OF THE CENTRE OF EQUIPONDERATION; OF
BODIES PRESSING DOWNWARDS IN STRAIT
PARALLEL LINES.
[1.] Definitions and suppositions.—[2.] Two planes of equiponderation are not parallel.—[3.] The centre of equiponderation is in every plane of equiponderation.—[4.] The moments of equal ponderants are to one another as their distances from the centre of the scale.—[5, 6.] The moments of unequal ponderants have their proportion to one another compounded of the proportions of their weights and distances from the centre of the scale.—[7.] If two ponderants have their weights and distances from the centre of the scale in reciprocal proportion, they are equally poised; and contrarily.—[8.] If the parts of any ponderant press the beams of the scale every where equally, all the parts cut off, reckoned from the centre of the scale, will have their moments in the same proportion with that of the parts of a triangle cut off from the vertex by strait lines parallel to the base.—[9.] The diameter of equiponderation of figures, which are deficient according to commensurable proportions of their altitudes and bases, divides the axis, so that the part taken next the vertex is to the other part of the complete figure to the deficient figure.—[10.] The diameter of equiponderation of the complement of the half of any of the said deficient figures, divides that line which is drawn through the vertex parallel to the base, so that the part next the vertex is to the other part as the complete figure to the complement.—[11.] The centre of equiponderation of the half of any of the deficient figures in the first row of the table of [art. 3], chap. XVII, may be found out by the numbers of the second row.—[12.] The centre of equiponderation of the half of any of the figures of the second row of the same table, may be found out by the numbers of the fourth row.—[13.] The centre of equiponderation of the half of any of the figures in the same table being known, the centre of the excess of the same figure above a triangle of the same altitude and base is also known.—[14.] The centre of equiponderation of a solid sector is in the axis so divided, that the part next the vertex be to the whole axis, wanting half the axis of the portion of the sphere, as 3 to 4.