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be established as tiie expression of that peculiar sensation wherever 

 it was found, and even to lose, in many cases, its original substan- 

 tive application. Various examples were given from our own lan- 

 guage, all tending to prove how apt the mind is to employ the 

 names of objects, not only to denote the aggregate of properties 

 which makes up the notion of that object, but occasionally also to 

 express its predominant and distinctive quality as it exists in a dif- 

 ferent substance, which has no other attribute in common with it. 



2. On Single and Correct Vision by means of Double and 

 Inverted Images on the Retinae. By D»' Alison. 



The author began by endeavouring to state with precision the 

 nature of the difficulty which has been long felt on this subject. 

 Two general fiicts are well ascertained, and present fair objects of 

 inquiry, 1. That images formed on corresponding points of the 

 retinae of the human eyes, and on these only, naturally affect the mind 

 in the same manner as a single image, formed on the retina of either 

 eye ; and, 2. That impressions made on different points of the re- 

 tina of the eye, are naturally followed by inferences as to the re- 

 lative position of the objects producing them, exactly opposite to 

 those which follow impressions made on different points of the sur- 

 face of the body. 



Facts observed by Dr Reid and others, and confirmed by per- 

 sonal observation, appear to the author quite sufficient to shew, in 

 opposition to the opinion of Berkeley and of Dr Brown, that these 

 phenomena cannot be explained by reference to experience and as- 

 sociation ; and the law of visible direction, regarded by some as an 

 explanation, is in fact only a general expression of these phenomena ; 

 and Dr Reid distinctly stated, when he laid down that law, that a 

 farther step was to be expected, and " a more general law of vision 

 might be discovered,' if we should come to know " the structure 

 and use of the choroid membrane, the optic nerves and brain, and 

 what impressions are made <m them by means of the pictures on the 

 retinae." 



The theory of Newton, which ascribes single vision by images 

 formed on corresponding points of the retina, to the circumstance of 

 the corresponding points of the retina being connected (by means of 

 a semi-decussation of the optic nerves at their commissure), with the 

 same points in the sensorimn, was next considered, and stated to be 



