192 Mr. S. Rowley on a New Theory of Vision. 



meter is horizontal. If one side of the strip were lower than 

 the other, it would be in a situation in which the electrical 

 forces are both feebler and more horizontal. The attractive 

 forces therefore tend to restore the transverse diameter to its 

 horizontal position, the repulsive forces tend to draw it from it ; 

 and which of them it will obey depends on whether the attrac- 

 tive or repulsive forces have the greater moment round the longer 

 axis of the strip. But if the moment of the repulsive forces pre- 

 ponderate, the plane of the strip becomes vertical, and any in- 

 equality of the jags along its sides will carry it up or down from 

 its position of equilibrium, so that it probably soon flies off. It 

 appears, therefore, to be only in those cases in which the moment 

 of the attractive forces preponderates that the experiment is likely 

 to succeed. Hence it would seem that a good shape for the strip 

 would be that of an arrow-head with a sharp point and two blunt 

 barbs. Finally, I have seen the strip take up a position several 

 centimetres below the knob, showing that even lines of force 

 which started from the stem curved upwards. 

 I am, Gentlemen, 



Your obedient Servant, 



G. Johnstone Stoney. 



XXVI. A New Theory of Vision. 

 By Samuel Rowley, M.A.* 



MY purpose in the following communication is to offer a 

 theory of vision which I believe has not been heretofore 

 advanced, and which I venture also to believe to be the true one. 

 But before entering upon its consideration it may be proper 

 briefly to state, with reasons for rejecting them, the theories 

 hitherto advanced. 



The theory of Aguilonius supposes that all the images im- 

 pressed on the retinse at any given instant are seen in a plane 

 perpendicular to the plane of the optic axes at their point of 

 convergence, and parallel to the line joining the centres of the 

 two pupils — and consequently that the two images of any object 

 situated in this plane, occupying, as they necessarily do, one and 

 the same place, are seen single with two eyes. 



If any person, whom a little practice has fitted to make such 

 experiments, will place at some short distance (say, 3 inches), 

 in a line parallel to the eyes two small objects, one directly 

 before the central point of the interval between the eyes, and 



* [We are indebted to the author for proof-sheets of this paper in advance 

 of the issue of the September Number of Silliman's Journal, to which it 

 was first communicated. Eds.] 



