It is true sketches, or such drawings as painters generally make for
their works, give this pleasure of imagination to a high degree. From a
slight, undetermined drawing, where the ideas of the composition and
character are, as I may say, only just touched upon, the imagination
supplies more than the painter himself, probably, could produce; and we
accordingly often find that the finished work disappoints the
expectation that was raised from the sketch; and this power of the
imagination is one of the causes of the great pleasure we have in
viewing a collection of drawings by great painters.
_Reynolds._