Subjective Sensations and Illusions. 829 



three as constituting a single machine, and supposing power f o be ap- 

 plied to the end dynamo ( and leaving friction, waste, &c. , out of the 

 account), we can imagine that dynamo to drive the middle one, and that 

 to turn the water-wheel backwards and lift" the water back to its posi- 

 tion above the dam. And so I take it, we may add a third term to the 

 machine composed of the brain organ and the retina, and that will be the 

 medium which conveys the force to the retina from the outside when 

 the action is in the usual direction. That medium is the ether whose 

 vibration normall} 7 sets up the action in the retina, which, transferred to 

 the brain, causes the sensation of light. Worked the contrary way, the 

 excitement of the brain organ by causes within the brain, sets the re- 

 tina into activity, which in turn communicates the motion to the ether 

 beyond. There is nothing violent in this hypothesis. It accords with 

 analogy that the relationship well known to exist between the energy 

 of an excited retina, and that of the light-bearing ether, may be recip- 

 rocal. Granting that it is, and that the action of the retina origi- 

 nating in the brain behind it, may communicate actual motion to the 

 ether in front of it, the experiments with the spy glass, mirror and 

 prism become easily explainable. Otherwise it is difficult to see how 

 the action wholly in the brain can produce there the sensation of - 

 image which can be reflected in a mirror outside of it. 



The sort of motion communicated to the ether by the eye is probably 

 of a nature similar to that projected from the pole of a magnet, which 

 makes an excursion as a positive current, and causes a return of a com- 

 plemental negative current, or vice versa. It is these rays of force or 

 energy thus darted forward from the eye that the prism, the spyglass 

 and the mirror deal with,, by refracting, converging or diverging ( mag- 

 nifying or minifying ) and reflecting them. It is by the return currents 

 to the eye of the subject that he becomes aware of the action of the in- 

 struments. The impressions he gets of the position, shape, size, &c. , 

 of his phantom may also arise in part, or whole, from sight stimulations 

 from the neighboring objects. ( See Darwin's experiment further on. ) 

 This theory supposes that these lines or rays of force can be reflected 

 and analyzed like light. There is strong reason to think the polar en- 

 ergies and light are movements of the same ethereal substance. Ner- 

 vous energy as it is manifested in the nerves, ganglions and brain, and 

 projected from the body into the space around it, is beyond reasonable 

 doubt, a motion of the same substance. The mode of the motion may 

 not be identical with either light or magnetism, and yet possess qualities 

 and capacities belonging to both. If the organ of the cerebral fancy 

 can thus disturb the onvironiin-nt. by a ival physical motion like that of 

 light or magnetism, it might reasonably IK- anticipated that the motion 

 would or could be communicated to another person so that he could be 



