980 Dynamic Theory. 



their own, and not a motion of the hot body; and that it is in fact a 

 part of their awn minds. In like manner we say we have a sensation 

 of red or of a sound, &c. , as if an object we looked at were red, or the 

 sound pertained to the sonorous bod}'. These are also parts of our 

 minds. We do not have a sensation of red, but we have a sensation 

 7*ed, and it is a sensation of ethereal undulations of a particular rapidity 

 and length. So white, cold, hot, bitter, sweet, sour, &c. , are motions 

 of our own brain, and do not belong to objects in the environment, al- 

 though they are the sequels of the motions of such objects. 



The intensity and quantity, then, of any sensation is in proportion to 

 the friction of the incoming stimulation that represents the amount of 

 it that is arrested and reduced to the new form of motion, sensation. 

 The process is generally accompanied by an increase of temperature in 

 the brain tissues, which increase may give a secondary sensation of 

 heat. This rise of temperature is due in part to the arrest of tones of 

 stimulation which do not arouse sensation, and in part to the additional 

 quantity of blood which is thrown into the brain upon every stimulation, 

 which establishes a temporary center of attention there. (See page 

 670.) 



Where the same stimulation continues to be monotonously repeated 

 for a considerable time, sensation of it ceases after a time, in spite of 

 the continued action of the stimulus. If the organs upon which the 

 stimulations play, were not wasted by the action upon them, the 

 consciousness would continue. But they become unable after a time to 

 be moved, and go to sleep, and although they are doubtless soon re- 

 paired, and although the stimulus keeps on, they are apt to sleep until 

 the stimulus stops and then a sensation is again aroused. Thus a per- 

 son sitting quiet in a mill will be put to sleep by its drowsy hum, but if 

 it stops, he will awake with a start. So, as observed by Bain, a watch- 

 maker is not aware of the continuous ticking of his clocks, but would 

 be quickly startled if they all suddenly stopped. We are strikingly re- 

 minded by this action, of the performance of the galvanic current in- 

 duced in a secondary coil upon the opening and closing of a primary, 

 as shown on page 332. We are probably not entirely unconscious of 

 the monotonous sound even when we seem to be, but keep a sub-conscious 

 reckoning of it as we do our natural sleep. After waking we have some 

 sort of notion whether the nap has been long or short. So the absence 

 of sensation of sound during stillness is different from the absence of 

 sensation produced by monotony. Yet we seem to have a sensation of 

 silence as if it were a positive quality. 



The sensation of black as a color is also due to the same principle. 

 White, yellow, red, &c. , are real sensations originating in real mo- 

 tions of ether in the objective environment. But black is simply silence 



