428 Mr. P. Cooper on Accidental Colours, 



the eye less sensible to its influence, when long exposed to 

 its action : for, if the latter be the case, the various pheno- 

 mena of accidental colours are necessary consequences ; 

 and, independently of the objection to the introduction of 

 a new principle, which has not been traced to any other 

 purpose, it would be contrary to the rules of philosophy to 

 admit two unconnected causes to account for one effect. 



Mr. Tomlinson objects to a comparison between the 

 functions of the eye and the palate, because the senses are 

 fitted for such opposite uses ; (7) but, when the analogy is 

 so general, and so complete, as in the present case, though 

 it may not furnish conclusive evidence, it is entitled to 

 some consideration. — ^Every person must have observed, 

 that the most nauseous smell in a short time becomes less 

 offensive ; and, that those who live in situations, which 

 expose them to nuisances of this kind, soon become quite 

 insensible to them. The same principle prevails with 

 scents of a more agreeable character ; we are frequently 

 delighted with the fragrance of a flower, but if we attempt 

 to prolong the passing gratification, it quickly degenerates, 

 and, if not intermitted, soon becomes insipid. — The sense 

 of feeling is liable to the same gradual decay after the first 

 impression ; the points of the fingers, which at first are 

 very susceptible of its influence, soon cease to convey any 

 sensation, unless the contact be intermitted, or otherwise 

 renewed ; the blind, whose sense of touch is very delicate, 

 when they endeavour to ascertain the qualities of bodies 

 through this medium, may be observed to keep their fingers 

 in constant motion. — The sense of hearing is also subject 

 to decay ; and most persons will recollect instances in 

 which sounds long continued have become almost, if not 

 quite inaudible. — The sense of taste exhibits this principle 

 in a striking manner ; and, from some few experiments 

 which I have made on the subject, I think it probable, that 

 the flavour of bodies, when their composition is not too 

 complicated, may be analyzed by means of it, upon the 

 same principle that we analyze compound light, by render- 

 ing the palate insensible to the different ingredients of 

 which it consists in succession : thus, strong tea sweetened, 

 so that neither flavour may prevail, will alternately become 

 sweet and astringent, if we render the palate insensible to 



