PERCEPTIONS OF ANIMALS. 571 



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 in- 

 adequate to observe. But neither our ther- 

 mometers, nor our electroscopes, our hygro- 

 meters, nor our galvanometers, however skilfully 

 devised or elaborately constructed, can vie in 

 delicacy and perfection with that refined appa- 

 ratus 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 per- 

 ceptions 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 conceive how the limits of visible colour 

 may be established ; for if there be no nervous 

 fibres in unison with vibrations more or less 

 frequent than certain limits, such vibrations, 

 though they reach the retina, will produce no 

 sensation. Thus it is perfectly possible that 

 insects, and other animals, may be incapable of 

 being affected by any of the colours which we 

 perceive ; while they may be susceptible of re- 

 ceiving distinct luminous impressions from a 



