46 ON GOETHE'S SCIENTIFIC RESEARCHES. 



movements, of attractive and repulsive forces, whose intricate 

 actions and reactions, though governed by strict laws, can 

 scarcely be taken in at a glance. To him the impressions ^of 

 sense are not an irrefragable authority ; he examines what claim 

 they have to be trusted ; he asks whether things which they 

 pronounce alike are really alike, and whether things which they 

 pronounce different are really different ; and often finds that he 

 must answer, no ! The result of such examination, as at present 

 understood, is that the organs of sense do indeed give us informa- 

 tion about external effects produced on them, but convey those 

 effects to our consciousness in a totally different form, so that 

 the character of a sensuous perception depends not so much on 

 the properties of the object perceived as on those of the organ 

 by which we receive the information. All that the optic nerve 

 conveys to us, it conveys under the form of a sensation of light, 

 whether it be the rays of the sun, or a blow in the eye, or an 

 electric current passing through it. Again, the auditory nerve 

 translates everything into phenomena of sound, the nerves of the 

 skin into sensations of temperature or touch. The same electric 

 current whose existence is indicated by the optic nerve as a flash 

 of light, or by the organ of taste as an acid flavour, excites in 

 the nerves of the skin the sensation of burning. The same ray 

 of sunshine, which is called light when it falls on the eye, we 

 call heat when it falls on the skin. But on the other hand, in 

 spite of their different effects upon our organisation, the daylight 

 which enters through our windows, and the heat radiated by an 

 iron stove, do not in reality differ more or less from each other 

 than the red and blue constituents of light. In fact, just as in 

 the Undulatory Theory the red rays are distinguished from the 

 blue rays only by their longer period of vibration, and their 

 smaller refrangibility, so the dark heat rays of the stove have a 

 still longer period and still smaller refrangibility than the red 

 rays of light, but are in every other respect exactly similar to 

 them. All these rays, whether luminous or non-luminous, have 

 heating properties, but only a certain number of them, to which 

 for that reason we give the name of light, can penetrate through 

 the transparent part of the eye to the optic nerve, and excite a 



