letter put into his hand whether it produces a sensibility equal to or under the standard. This, too, is a result preeminently intellectual in its nature; the process of acquisition that brings it about, ranks as a fundamental property of our intelligence. The sensibilities that can assume this permanent character, so as to be used in comparison, without the presence of their original cause, are truly intellectual sensibilities.

The sensitiveness to relative weight, or to things actually compared together, may not imply great sensitiveness to absolute weight, which involves a greater or less degree of retentiveness or memory.

Although the use of the balance supersedes, to a very great extent, the sensibility to weight residing in the muscular system, there are occasions where this sensibility can display its acuteness. In many manual operations, weight is often estimated without the aid of the balance. In throwing a missile to reach a mark, an estimate of weight must enter into the computation of the force expended.

In appreciating the cohesiveness of tenacious bodies-the thickness of a dough, or the toughness of a clay-the same sense of resistance comes into operation. In like manner, the elasticity of elastic substances—the strength of a spring, the rebound of a cushion-can be discriminated with more or less nicety.

23. The second mode of muscular discrimination respects the Continuance of it. A Dead Strain of unvarying amount being supposed, we are differently affected according to its duration. If we make a push lasting a quarter of a minute, and, after an interval, renew it for half a minute, there is a difference in the consciousness of the two efforts. The endurance implies an increased expenditure of power in a particular mode, and we are distinctly aware of such an increase. We know also that it is not the same as an increase in the intensity of the strain. The two modes of increase are not only discriminated as regards degree, they are also felt to be different modes. The one is our feeling

and measure of Resistance or Force, the other stands for a measure of Time. All impressions made on the mind, whether those of muscular energy, or those of the ordinary senses, are felt differently according as they endure for a longer or a shorter time. This is true of the higher emotions also. The continuance of a mental state must be discriminated by us from the very dawn of consciousness, and hence our estimate of time is one of the earliest of our mental aptitudes. It attaches to every feeling that we possess.

The estimate of continuance attaches to dead resistances, but not to that alone. When we put forth power to cause Movement, as in lifting a weight off the ground, or in pulling an oar, we are aware of a difference in the continuance of the movement. We also know that we are moving, and not simply resisting. The two modes of exercising force are not confounded in our consciousness; we hold them as different, and recognize each when it occurs. Now, the continuance of movement expresses more to us than the continuance of a dead strain. It is the sweep of the organ through space, and connects itself, therefore, with the measure of space or extension. The range of a muscle's contraction, which is the same as the range or extent of motion of the part moved, is appreciated by us through the fact of continuance. Being conscious of a greater or less continuance of movement, we are prepared for estimating the greater or less extent of the space moved through. This is the first step, the elementary sensibility, in our knowledge of space. And, although we must combine sensations of the senses with sweep of movement, in our perception of the extended, yet the essential part of the cognition is furnished by the feelings of movement. We learn to know, by a process to be afterwards adverted to, the difference between the co-existing and the successive, between Space and Time; and we can then, by muscular sweep-that is, by the continuance of muscular movement-discriminate the differences of extended matter or space. This sensibility becomes a means of imparting to us in the first place the feeling of linear

extension, as measured by the sweep of a limb, or other organ moved by muscles. The difference between six inches and eighteen inches is represented by the different degrees of contraction of some one group of muscles; those, for example, that flex the arm, or, in walking, those that flex or extend the lower limb. The inward impression corresponding to the outward fact of six inches in length, is an impression arising from the continued shortening of a muscle. It is the impression of a muscular movement having a certain continuance; a greater linear magnitude is a greater continuance.

The discrimination of length in any one direction obviously includes extension in every direction. Whether it be length, breadth, or height, the perception has precisely the same character. Hence superficial and solid dimensions, the size or magnitude of a solid object, come to be felt through the same fundamental sensibility to expended muscular force. All this will be understood more fully at an after stage, when we shall have to consider muscularity in connexion with the senses of Touch and Sight.

By means of the muscular sensibility associated with prolonged contraction, we can thus discriminate different degrees of the attribute of space, in other words, difference of length, surface, and form. When comparing two different lengths, we can feel which is the greater, just as in comparing two different weights or resistances. We can also, as in the case of weight, acquire some absolute standard of comparison, through the permanency of impressions sufficiently often repeated. We can engrain the feeling of contraction of the muscles of the lower limb due to a pace of thirty inches, and can say that some one given pace is less or more than this amount. According to the delicacy of the muscular organs, we can, by shorter or longer practice, acquire distinct impressions for every standard dimension, and can decide at once as to whether a given length is four inches or four and a half, nine or ten, twenty or twenty-one. A delicate sensibility to size is an acquirement suited to many mechanical opera

RAPIDITY OF MOVEMENT.

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tions; as in drawing, painting, and engraving, and in the plastic arts.

24. Under the foregoing head, we supposed the case of steady or uniform movement; and called attention to the power of discriminating the greater or less continuance of it. But movements may vary in their rate of Speed; and it is now to be considered whether or not the mind is affected when the speed is increased or diminished. This is also a mode of expending additional power; and it is not possible for us to increase the expended energy without being conscious of the fact. The only doubt that might arise is as to our being able to distinguish the various modes of increaseincrease in the dead strain at any one instant, increase in the duration of the strain, increase in the duration of a movement, increase in the velocity of the movement-so as to be aware which mode we are under for the time. If we confounded all

these modes of increase under a common impression of intensified energy, our muscular discrimination would be wholly inadequate to the perception of the external world; and, in particular, our ability to estimate extension would have to be referred to some other part of our constitution. But it is quite certain that we are differently affected under these various situations. Our consciousness is not the same when we augment the energy of a dead resistance, as when we protract the time of that resistance; nor is it the same when we prolong the duration of a uniform movement, and when we add to its speed. We are aware, when we accelerate our pace, not merely that more power is going out of us, but that such power is in one especial mode, which we distinguish from other special modes. This being assumed, we are cognizant of degree in the rapidity of our movements, and so possess the power of estimating another great property of moving bodies, the velocity of their motions. This measure is taken first on our own movements, and thence extended to other moving things that we encounter. When we follow a moving object with the hand, or with the eye, or keep pace with it, its velocity is transferred to ourselves, and estimated accordingly.

The feeling of the rapidity of muscular contraction has a further office. It is an additional means of measuring Extension. An increase of velocity in the same time corresponds to an increase of range or extension, no less than the same velocity continued for a greater time. Extent of Space thus, connects itself with two separate discriminations-Continuance, and Velocity, of movement.

The distinct feelings from the various forms of muscular exercise, as formerly explained, whereby we are differently affected according as movement is slow or quick, are thus of great intellectual importance, as enabling us to be characteristically impressed by each varying degree of velocity. The soothing tendency of the slow motions, and the exciting effect of the comparatively rapid motions, are instrumental in enabling us to discriminate degrees of velocity directly, and of space indirectly.*

* A fourth variety of muscular discrimination may be pointed out as in constant use, namely, the sense of the amount of contraction of a muscle, and of the position of the limb in consequence. We are ordinarily aware not merely that we are putting forth a force of a certain degree and continuance, but that we are operating either at the beginning of the muscle's contraction, so to speak, or at some advanced stage of the contraction. This determines, of course, the attitude or position of the part moved. We know, in exerting the arm in the dark, whether it is extended or bent, and whether it is thrown before or behind. We know in grasping anything in the hand, whether the hand is very much stretched, or very much closed; and we can judge of the different degrees of contraction determining intermediate positions.

By this sensibility we are able, after experience, to estimate the magnitudes of bodies without moving the arm or the hand, or other organ. By the mere stretching of the arms, without attending to the movement implied in that stretch, we measure in our mind the length of an object, or of an interval. By the dead span of the fingers and thumb, we can estimate any length that is within the scope of the parts.

It is usual to describe this particular discrimination as a sense of the state of the muscle's contraction, and to regard it as the primary or typical form of the muscular sense. Now, the discrimination must no doubt be an original fact; one cannot see how it could be acquired; but the meaning given to it, the interpretation of the position of the limb, and of the magnitudes embraced between two outstretched parts, is wholly acquired. We must learn by experience what movements correspond to the transition from one mode of contraction to the other; extension must be measured first by movement. A definite fixed position of the two arms, of the two legs, of the jaws, of the