284 tAY SERMONS, ESSAYS, AND REVIEWS. [xiv. 



singularly delicate apparatus, connected with the termination of 

 the fibres of the optic nerve. The impulses of the attenuated 

 matter, or ether, affect this apparatus and the fibres of the optic 

 nerve in a certain way ; and the change in the fibres of the optic 

 nerve produces yet other changes in the brain ; and these, in 

 some fashion unknown to us, give rise to the feeling, or con 

 sciousness, of redness. If the marble could remain unchanged, 

 and either the rate of vibration of the ether, or the nature of 

 the retina, could be altered, the marble would seem not red, but 

 some other colour. There are many people who are what are 

 called colour-blind, being unable to distinguish one colour from 

 another. Such an one might declare our marble to be green ; 

 and he would be quite as right in saying that it is green, as we 

 are in declaring it to be red. But then, as the marble cannot, 

 in itself, be both green and red, at the same time, this shows 

 that the quality &quot;redness&quot; must be in our consciousness and 

 not in the marble. 



In like manner, it is easy to see that the roundness and the 

 hardness are forms of our consciousness, belonging to the groups 

 which we call sensations of sight and touch. If the surface of 

 the cornea were cylindrical, we should have a very different 

 notion of a round body from that which we possess now ; and if 

 the strength of the fabric, and the force of the muscles, of the 

 body were increased a hundredfold, our marble would seem to 

 be as soft as a pellet of bread crumbs. 



Not only is it obvious that all these qualities are in us, but, if 

 you will make the attempt, you will find it quite impossible to 

 conceive of &quot; blueness,&quot; &quot; roundness,&quot; and &quot; hardness &quot; as existing 

 without reference to some such consciousness as our own. It 

 may seem strange to say that even the &quot; singleness &quot; of the 

 marble is relative to us ; but extremely simple experiments will 

 show that such is veritably the case, and that our two most 

 trustworthy senses may be made to contradict one another on 

 this very point. Hold the marble between the finger and 

 thumb, and look at it in the ordinary way. Sight and touch 

 agree that i is single. Now squint, and sight tells you that 



