cii. XV.] THE COMPOSITION OF MIND. 129 



tion is either of contact or of temperature; in the second case, 

 there is a sensation of resistance or pressure; and in Loth 

 cases, when the sensation proper to the nerve is prolonged or 

 intensified beyond a certain degree, it is at first acccmpanied 

 and finally supplanted by a sensation of pain. Now, Weber's 

 experiments have shown that these differences in sensation 

 are not due to the excitation of distinct nerves, but to the 

 differently-combined excitation of the filaments of the same 

 nerves. The difference between the sensation of contact and 

 the sensation of temperature depends upon the order in which 

 the filaments of a particular nerve are set in vibration. And 

 thus, as Fick observes, we may understand why it is difficult 

 to distinguish between a prick from a needle and a minute 

 burn from a spark of fire; for the nearer we approach to a 

 truly elementary sensation, the more evanescent becomes the 

 distinction between the compound sensation of temperature and 

 that of mechanical contact. On the contrary, when a larger 

 area of skin is suddenly rubbed or burnt, so that enough nerves 

 are brought into play to compound the elements of the sensa- 

 tions, then there is no difficulty in distinguishing the feeling 

 of temperature from that of mechanical contact. From these 

 and many other kindred facts, to which scanty justice is done 

 by this cursory allusion, M. Taine very plausibly concludes 

 that our ordinary tactile sensations are made up of little 

 component psychical affections differing only in number, 

 order, and duration ; while, according as these elementary 

 psychical states are differently compounded, they form con- 

 scious sensations which, as presented to consciousness, seem 

 to be severally simple and distinct in kind. 



Throughout this remarkable analysis questions are sug- 

 gested which can be completely answered only when physics 

 and chemistry, as well as physiology and psychology, are 

 much more advanced than at present. Yet there are three 

 Important principles which we may regard as established in 

 the case of sound, and as clearly indicated in the case of the 



VOL. II. K 



