But ‘tis not enough that the Colours in themselves are Beautiful singly, and that there be Variety, They must be set by one another so as to be mutually assistant to each other ; and this not only in the Object painted, but in the Ground, and whatsoever comes into the Composition ; so as that every Part, and the Whole together may have a pleasing effect to the Eye ; such a Harmony to It as a good piece of Musick has to the Ear ; But for which no certain Rules can be given no more than for that : Except in some few General Cases which are very Obvious, and need not therefore be mention’d here.