512 THE SENSORIAL FUNCTIONS. 



from those whicli the same objects communicate to 

 ourselves. While with regard to distance and mag- 

 nitude our perceptions take a wider range, and 

 ap})ear infinitely extended when compared with 

 those of insects, yet they may, in other respects, 

 be greatly inferior. The delicate discrimination of 

 the more subtle affections of matter is perhaps com- 

 patible only with a minute scale of organization. 

 Thus the varying degrees of moisture or dryness 

 of the atmosphere, the continual changes in its 

 pressure, the fluctuations in its electrical state, and 

 various other physical conditions, may be objects 

 of distinct perception to these minute animals. 

 Organs may exist in them, appropriated to receive 

 impressions, of which we can have no idea ; and 

 opening avenues to various kinds of knowledge, to 

 which we must ever remain utter strangers. Art, 

 it is true, has supplied us with instruments for dis- 

 covering and measuring many of the properties of 

 matter, which our unassisted senses are inadequate 

 to observe. But neither our thermometers, nor our 

 electroscopes, our hygrometers, nor our galvano- 

 meters, however skilfully devised or elaborately 

 constructed, can vie in delicacy and perfection 

 with that refined apparatus of the senses, which 

 nature has bestowed on even the minutest insect. 

 There is reason to believe, as Dr. Wollaston has 

 shown, that the hearing of insects comprehends a 

 range of perceptions very different from that of the 

 same sense in the larger animals ; and that a class 

 of vibrations too rapid to excite our auditory nerves, 

 is perfectly audible to them. Sir John Herschel 

 has also very clearly proved that, if we admit the 

 truth of the undulatory theory of light, it is easy to 



