392 Royal Society : — 



argument, finally, seems irrefragable : engraver and painter 

 succeed in presenting, the one the form, and the other the form 

 and colour of the sky as we really perceive them by the sense, 

 their success depending solely on an observed law of perspective, 

 which mathematically demonstrates the sky they depict at the 

 horizon to be further considerably than that they represent at 

 the zenith. Now the senses, in recognizing the truth of this 

 representation of the sense-perceived form of the sky, assert 

 unequivocally what the sense-perception is. 



It remains to show, B, that the apparent distance of the 

 luminary coincides with that of the sky. It may be argued, 

 since there is no sensory evidence of the actual distance of the 

 luminary, 1st, that the sense can only refer it to the ground which 

 surrounds it ; 2nd, that, by the universal law determining 

 visual distance with one or both eyes, no object is felt to be 

 beyond or in advance of another surrounding it, unless, the size, 

 parts, texture, or colour of both being known or assumed, the 

 sight detects that one is more obscured than the other, in which 

 case the less obscured is inferred to be less distant, and vice 

 versa; 3rd, a strong light, placed at any distance behind a hole 

 in a semi -illuminated screen, appears to fill the aperture and be 

 there situate ; or a sunbeam piercing an interstice appears to 

 emanate from the object in which the interstice exists. 



If, then, the positions A and B are established, it follows 

 that the luminary in the zenith appears nearer than at horizon ; 

 and, subtending (practically) the same angle in both cases, it is 

 hardly necessary to add (what my paper referred to sets forth) 

 that when the luminary is supposed to be nearer it is necessarily 

 perceived to be smaller. 



Trusting you will excuse the unforeseen length of this explana- 

 tion of my views, perhaps somewhat misunderstood by you r 

 correspondent, Believe me to be, Sir, 



Yours very respectfully, 



T. Zeno. 



MIL Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 322.] 



November 21, 1861. — Sir Benjamin Collins Brodie, Bart., President, 



in the Chair. 

 f I^HE following communications were read : — 



J. " Note on the Oxidation and Disoxidation effected by the Per- 

 oxide of Hydrogen." By B. C. Brodie, F.R.S., Professor of Che- 

 mistry in the University of Oxford. 



In a former communication* I laid before the Society a detailed 



* Phil. Trans, ii. 1850, 759. 



