THE PLEASURES OF VISUAL FORM. 785 



most obvious way of realizing such smoothness is by reducing the 

 degree of change or contrast to a minimum. In this way we get 

 a gradation of movement either in respect of velocity or of di- 

 rection. 



Gradation in du-ection or velocity, like gradation in shade of color 

 or pitch of tone, is attended by a peculiarly agreeable feeling. One 

 and the same movement may exhibit a gradual rise and fall of velocity, 

 and it is probable that this is the form of movement naturally pro- 

 duced by all muscular contraction. Gradation in direction, which is 

 at the basis of all curvilinear movements, depends on a gradual altera- 

 tion in the relative degrees of activity of two or more muscles, and 

 so corresponds to gradation in color or tone, which is supposed to rest 

 on a continual increase of activity in certain nerve-elements, and de- 

 crease in others. A mode of gradation somewhat similar to that in 

 direction is experienced in symmetrical movements of convergence, 

 and especially in moving the axes from a near to a distant point, and 

 so gradually relaxing the tension due to convergence.* 



This mode of motor enjoyment is realized when standing in the 

 middle of a building or an avenue of trees, and tracing an imaginary 

 central receding line, and it is noticeable that we naturally place our- 

 selves in the position and execute this kind of movement whenever 

 we wish to appreciate the effect of perspective. It may be added that 

 a union of gradation of velocity with that of duration, as in tracing 

 the path of a projectile across the field of vision, affords the eye its 

 richest form of motor delight. 



A graduated series of movements allows of the least exciting de- 

 gree of the feeling of variety. If a more powerful effect of change 

 is desired, the element of smoothness must be looked for in another 

 way. A succession of different movements has a cei'tain degree of 

 smoothness if they are continuous and free from sudden pauses and 

 jerkiness. This can only happen if the movement is continuous in 

 time, and, what is implied in this, in space — that is to say, the second 

 movement must be one which can be commenced in that jDosition of 

 the eye in which the first has left it. Where this is not the case, 

 there must be a "sirring," so to speak, of the eye, to the new starting- 

 point, which counts as an appreciable element of roughness or un- 

 evenness. 



A higher degree of fluency is attained when the muscles, succes- 

 sively employed, are organically connected one with another, whether 

 by some innate arrangement or by the influence of habit. This ap- 

 plies more especially to the action of the antagonists. A movement 

 of the eyes to the left of the field produces a tendency in the antago- 

 nists to pull them back again. Hence the natural disposition to trace 



* A rectilinear movement of the eye away from and back to the primary position may • 

 be said to afPord a faint feeling of gradation, analogous to that experienced in movementa 

 of convergence. 



VOL. XVI. — 50 



