The remarks in 372 are applicable here also, as are those of 374. The best executed, and in the best taste, are those with black figures, or of figures much darker than the ground. Paper-hangings, I do not say the most tasteful, but those most convenient for use, present very light grounds, with white or grey figures. 379. Grey patterns, upon papers tinted of a light colour, exhibit the phenomenon of maximum contrast; that is to say, the grey appears coloured with the complementary of the ground. [Illustration: PLATE XIV.] Thus, conformably to the law, (Plate 14) Grey patterns upon a _Rose_ ground appear _Green_. ” ” ” an _Orange_ ” ” _Blue_. ” ” ” a _Yellow_ ” ” _Violet or Lilac_. ” ” ” a _Green_ ” ” _Rose_. ” ” ” a _Blue_ ” ” _Orange-grey_. ” ” ” a _Violet_ ” ” _Yellow_. 380. I mention these examples to instruct artists, for, in manufactories of paper-hangings, disputes arise between the proprietors and the preparers of the colours. For instance, a few years ago, the proprietors of one of the first manufactories in Paris, wishing to print grey patterns upon grounds of apple green and of rose, refused to believe that his colour preparer had given any _grey_ to the printer, because the designs printed on these grounds appeared coloured with the complementaries of the colour of the ground. It was only when the colour preparer, having attended a lecture I gave for M. Vauquelin, at the Museum of Natural History, and hearing me speak of the mistakes that these contrasts of colours might occasion, suspected the cause of the effects which he had unconsciously produced, and which had really caused him much annoyance. OF THE LAW OF SIMULTANEOUS CONTRAST OF COLOURS RELATIVELY TO THE BORDERS OF PAPER-HANGINGS. 381. Every paper of one colour, or one belonging to the second category, should receive a border generally darker and more complex in design and colour than the paper which it frames. The assortment of two papers exercises a very great influence on the effects they are capable of producing; for each of them may be of a fine colour, ornamented with designs in the best taste, yet their effect will be mediocre, or even bad, because the assortment will not be conformable to the law of contrast.