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XIII.— ON" EQUAL TEMPEEAMENT, AND ON THE CAUSE OP 

 THE EFEECT UPON PIANO MUSIC PEODUCED BY 

 THE KEY IN WHICH IT IS SET. By G. JOHNSTONE 

 STONEY, D. Sc, F.E.S., a Vice-President of the Society. 



[Eead, March 19, 1883.] 



Perhaps of all the canons of Art, that one is the most important 

 which declares that correctness in Art is not identical with accuracy 

 in Mathematics. It would be no just criticism of the outline of a 

 drawing to say that inaccuracies could be detected with a micro- 

 scope. Correctness in a work of Art has been fully attained when 

 the deviations have been kept below what can be noticed by 

 the human beings who are to be impressed by that work of Art. 

 Hence in Art a latitude within certain narrow bounds is not only 

 allowable, but commendable. Even when no other advantage is 

 gained by it, the tolerance of it, at all events, preserves the artist 

 from misapplying his powers. 



But there are cases where new artistic effects of importance can 

 be obtained by deviations, and then they deserve to be commended 

 on other ground, and in a higher degree. Thus, in the pictorial 

 Art, that part of the appearance of standing out in relief which 

 is given to natural objects by what astronomers call parallax is 

 absent. All the objects in the painting are necessarily in one 

 plane, and we cannot judge of their distances by our binocular 

 vision, or by slightly moving our heads, as we habitually do judge 

 of the distances of natural objects. Hence the artist is only able 

 to suggest these distances by the sizes of the objects in his picture, 

 and by the colours, lights, and shades he throws over them — the 

 parallactic element is necessarily absent. 



If the artist augments the effect produced by colours, lights, 

 and shades beyond what exists in natural objects, he can in part 

 supply the place of the absent element ; and, if he avails himself 

 of this resource with skill and moderation, the augmentation falls 

 within such narrow limits, that it is not felt by the beholder as a 



SCIEN. PROC, B.D.S. VOL. IV. PT. II. G 



