Literary Notices. 139 



and in others, with limitations . that bring it more in accordance 

 with the opinions usually held. Mr. Abbott says, "when we look 

 from a near object to one a little farther off, the ocular adjustment 

 is accompanied with a certain motion more suitable indeed than that 

 of the hand to suggest distance ; because for the same distance it is 

 always the same ; but still only a succession. But the former ob- 

 ject continues to be seen, although with decreasing distinctness. 

 Through a certain short interval both objects may be seen dis- 

 tinctly. This co-existence demands the idea of space as the indis- 

 pensable form of its intuition. But what space ? Not the 

 superficial extension already known, the perception of which is 

 accompanied with a totally distinct sensation. Suppose, for ex- 

 ample, such a figure as a cube or the letter L placed on the table so 

 that the horizontal line is directed towards us. In looking along 

 the vertical line we are aware of the co-existence of certain dis- 

 tinctly visible parts, and by a certain motion can bring each in suc- 

 cession into the axis of vision. Thus we pass by a continuous 

 change to the foot of the vertical. Now it will be proved presently 

 that the eye requires a varying adjustment, in order to see dis- 

 tinctly at different distances. In moving the eye therefore along 

 the horizontal line we find a new kind of sensation added to the 

 former, and we also find the previously seen parts continue to be 

 seen, but with a quite different kind of distinctness from before. If 

 the horizontal line be near and long enough the parts not directly 

 looked at will be seen double ; and this will furnish another pecu- 

 liar antecedent. Here then first are the conditions for the percep- 

 tion of trinal extension." The description given here is 

 not that of seeing distance, but that of seeing different 

 things, or different portions of the same thing in linear suc- 

 cession. Mr. Abbott appears to us mistaken in the extent of 

 his denial, that we have to learn to see, and do so with the help of 

 touch and locomotion. Many distinguished reasoners on this sub- 

 ject have not adequately considered the various motions and adjust- 

 ments of which the eye is susceptible, and with which it can per- 

 form optical experiments, and thus obtain a series of sensations 

 indicative of extension in three directions, or of distance. Some 

 passages which Mr. Abbott quotes and objects to, are likewise not 

 sufficiently explicit, as where Mr. J. S. Mill states, " The informa- 

 tion obtained through the eye consists of two things — sensations, 

 and inferences from those sensations ; that the sensations are merely 

 colours variously arranged, and changes of colour." We presume 

 Mr. Mill, though incorrectly, includes simple light and shade under 

 the term colour, but the " colours variously arranged," are arranged 

 on the retina in definite forms, so that in certain positions of visual 

 objects, the apparent form and the real one will coincide. Again, 

 when Mr. Mill observes, " we judge an object to be some distance 

 from us by the diminution of its apparent magnitude, that is by 

 linear perspective, or by that dimness and faintness of colour and 

 outline which generally increases with the distance, in other words, 

 by aerial perspective ;" he omits to notice the adjustments of the 

 eye for binocular vision, and those required to bring divergent, or 



