ILLUSION. 475 ILLUSTRATION. objects, the single marble is 'felt' as two. This illusion of localization is described by Aristotle, in his tract On Dreams. (c) Draw a given length of coarse thread between the finger and thumb, at first slowly, and then more quickly. The thread appears to be much longer in the for- mer ca.se; the .separate 'pressure sensations have a longer time in which to run their course un- disturbed by subsequent pressures, and fullness of sensation is interpreted as length of thread, (d) If a point be moved over the skin at a uni- form rate, it will seem to travel more quickly as it crosses areas of greater sensitivity, and to become slow again as it enters regions of less sensitivity. A striking illusion of temperature is described by the English philosopher Locke (q.v.). Hold the one iiand in a bowl of heated, the other in a bowl of cold water. After a short time, plunge both hands into a bowl of lukewarm water. This will appear hot to the cooled, and cold to the heated hand. The illusion is due to the pre- ceding adaptation of the temperature-organs of the skin. (See Cutakeous Sensation.) An equally striking illusion in the sphere of kin- a-sthetic sensation is afforded by the fact that a small weight always appears heavier than a larger weight of the same objective lieaviness. The smaller weight stimulates intensively a lim- ited cutaneous area, with its underlying tissues; the larger weight stimulates lightly a large area of skin, and leaves the underlying tissues prac- tically unaffected. These instances, which could be multiplied almost indefinitely, show clearly that the term 'illusion' implies nothing more than a discrepancy between perception and ob- jective measurement. BiBLioriEAniv. For (1), consult Wundt, Physiolofiische ['sychologie (Leipzig, 18!1.3). (See Hallucination.) For (2), consult: Titehencr, Experimental Psychology (New York, 1901); Sanford, Course in Experimental Psychology (Boston, 1808); Wundt, Die geometrisch-opti- schen Tiiuschungen {"Leipzig, 1898) ; Lipps, /?««m- (Bsthetik vnd geometrisch-optische Tiiuschungen (Leipzig, 1807) ; .James, Principles of Psychology (New York, 1800) ; Hoppe, Psychologiscli-physio- logische Optik (Leipzig, 1881). ILLUSION COMIQUE, eTu'zySN' kA'mek', L' (Fr., till' comic illusion). A complicated and improbable play by Corneille (163G) embracing a comedy and a tragedy. ILLUSIONS, Optical. See Illusion. ILLUSIONS PERDUES, e'ln'zyON' par'di.i'", Les (I-'r., The Lost Illusions). A work in three parts by Balzac (18.37-43), which earned the hostility of the press by reason of its picture of the feuilletonists. ILLUSTRATED LONDON NEWS. The oldest illustrated weekly, founded in 1842, by Herbert Ingram. ILLUSTRATION. A term generally used in reference to the pictorial decoration and illustra- tion of books. In the more usual sense, book illustration is the addition to a book of pic- tures (and indirectly of maps and plans) which may aid in the riglit understanding of the text. This sen'ico they may render in a serious and almost scientific way by giving views of build- ings, accurate drawings or other reproductions of dress, portraits of individuals, copies of works Vol. X.— 31. of art named, and the like, these being things which are impossible to describe in words, and of which a clear presentation to the reader is de- sired. On the other hand, the illustrations may also be merely extensions of the te.t; thus, when Cruikshank or Leech illustrates Oliver Twist or Mr. Jorrock's Hunt, the description or narra- tive passage of the te.Kt is in a .sense repeated by the artist — a jiart of the story is retold in line and light and shade. A book consisting almost entirely of pictures, or having those for its principal subject, cannot be said to be an illustrated book. Thus the vol- umes of the Paris Salon, with large photograv- ures of the paintings and statuary of the year with a te.xt which is rather perfunctory, or that little volume which made the delight of school- boj's fifty years ago, Mr. Jonathan Oldhuck, or in more recent times, the albums of Caran D'Ache and Foiain, or Howard Pyle's or T. S. Sullivant's "Fables" are of this class. In the one case the pictures are the book, and the text is not absolutely needed; in the other ease the pictures and the brief legends or the re-written .Esop Fable a hundred words long, form together a humorous study of which the picture ib much the more important part. This is hardly illus- tration. And in like manner when the pictures drawn for a book are large, and few in number, and are printed on separate plates and bound in, they have less the air of illustration, and indeed, serve less well their purpose as illustration, than those which, being smaller, are inserted in the text. The very admirable pictures by Alljert Lynch given with the quarto edition of Maupas- sant's Pierre et Jean, although spoken of with great respect by excellent judges, and although admirable compositions, are yet less effective as illustrations than the le.'ss ]iretentious and really less able drawings by Jlerbach. and others which ore scattered through the duodecimo volumes of Paudet's L'Intmortel or Bourget's Mensonges, and immeasurably inferior to the roughly cut headpieces by Meissonier in Les coyitcs remois. From this point of view the famous 'vignettes' of the eighteenth century illustrated books are the least satisfactory of illustrations. They render, indeed, a single scene or incident of the story, but they are wholly unrealistic in char- acter, the figures being posed without general fruth of attitude or truth of gesture, and while they are attractive and instructive as works of the draughtsman and of the engraver's art. they are also models of all that is to be avoided in book illustration. History. The history of illustration is hard to treat as a continuous narrative. The Egj"p- tian manuscript Books of the Dead contain numl>ers of delicate and very ornamental paint- ings, usually of small size and combined with the text in an admirible way: and the paintings in the Ani Papyrus in the British ^luseuni, and a few other recently discovered manuscripts, have larger drawings. On the other hand, we are without any knowledge of Greek manuscripts with drawings accomiianying them. Of Roman Imperial manuscripts with illustrations there is nothing known prior to the Christian epoch: but the paintings which accompany the famous Ccnrsis of the Vienna IVIuseuni and a very few contemporary books remain to us. It is the opinion of excellent critics that these monuments of a decadent epoch will mislead us, if we try to
