BLIND. 178 BLIND SPOT. 'see' what they have accomplished. In the use of the parquetry, the circles, squares, etc., are not pasted on plain paper, as is usual in the kindergarten, but square and oblong cards of different sizes with raised lines, forminj; inch squares, printed on them have been substituted. Bibliography. Anagnos, Edtication of the Blind: nistoiical Shclch of Its Ocif/i'n, Rise, and Proyrcss (Boston, 1882); Ilaiiy, JJssai nur Vcdiicaiion- des aveugles (Paris, 1786) ; Niebo- quet, Des aveti'iles et de Icur education (Paris, 1837) : St. ilarie, Dcr Blinde vnd seine Bildung (Leipzig. 18US); Armitage, The Education and Kmploiiment of the Blind (London, 1871) : Moon, Light for the Blind (Loudon, 1873) ; Rosner, Vnterricht dcr Blindcn (Essen, 1877) ; Mell, En- cylclopiidixches Ihwdhuch des BUndenwesens (Vi- enna, ISDD-inOO). Consult also the Blinden- freuml (published at Diiren since 1881) and he Valentin Haiiy (edited by Maurice de la Size- ranne ) . BLIND, blint, lv.RL (1826—). A Gennan a"itator and writer. He was born at Mannheim, and while a student at Heidelberg was impris- oned for his revolutionary activity. In 1848 he i)arlieipated in the uprising in Baden, and had to llee, wounded. The next year he joined the band of liberals headed by Svruve which invaded south- ern Germany. He' was taken prisoner and sen- tenced to eight years' confinement. He was, how- ever, set free bv the populace and went to Karls- ruhe', whence he was sent by the Provisional Government as an envoy to Paris. Expelled from France, he went to Brussels, and then (1852) to London, where he found rest. There, for many years, he kept up his' political agitation through articles in many journals, and in intercourse with Garibaldi, Mazzini, Louis Blane, and other democratic leaders; but after 1806 his writings became less revolutionary in tone, in consequence, jicrliaps, of the death of'his stepson, wlio in May of that year attempted to assassinate Bismarck, and conunitted suicide in prison. Blind published a great number of political essays and l)rief arti- cles on history, mythology, and German litera- ture. Among bis works are: Fire-Burial Among Our flerman Forefathers: A Record of the Poetry and History of Teutonic Cremations; Ygdrasd: or. The Teutonic Tree of Existence; and biogra- Ijh'ies of Freiligrath, Ledru-Rollin, and Francis Deak. In 1807 he contributed an autobiograph- ical sketch to the C'ornhill Magazine, London. BLINDAGE (from hlind, in the sense of in- visilile, making invisible, as in 'blind story'). -V screen to shelter troops from an enemy's fire, it may be- constructed of lumber and earth, or of trees inclined against walls, or toward each other; much will depen<l on the available mate- rials and ingenuity of construction. The effect- ive defense of Ladvsmith, Kimberley, and Mafe- king. in the Boer War of lSnil-1902. was rendered largely possible by the clever construction and use of improvised bombproofs and shelters. See FOHTU'ICATION. BLIND BEGGAB OE ALEXAN'DRIA, Ttik. See CmAI'MAX. Gkohce. BLIND BEGGAB'S DAUGHTER OF BETHNAL GREEN. An English ballad in two ]iarts. of t)ie time of Queen Elizabeth. The blind beggar has a fair daughter, Bessie, whom a knight falls in love with, and marries. At the wedding-feast the blind beggar turns out to be Henry, son of Sir Simon de Montfort. Day. in IGo!)," and Ivnowles, in 1834, produced dramas entitled The Blind Beggar of Bethnal Green, founded on this poem. BLIND FISHES (of Caves) . See Cave-Ani- iI.LS. BLINDNESS. Want of sight may arise from any cau>e within the eye intercepting the rays of light on their way to the optic nerve, or from disease, defect, or injury of the optic nerve or optic tracts, or of the visual centres in the brain. Blindness may exist from birth, or be acquired. It may be present during the day or the night, and may be permanent or transient, complete or partial. Congenital Blindness is due to deficient development of the nervous appa- ratus or to defect in the globe; to cataract (q.v. ) ; to defect or disease of the cornea, choroid coat, optic nerve, or retina; or to tumors. Acquired Blindness may be due to injury of the eye or ^vounds of the head, or operations, or sympa- thetic irritation; to ophthalmia neonatorum, trachoma, diseases of the cornea, iris, choroid, or retina; to glaucoma or tumors; or to Bright's disease of the kidneys, heart disease, syphilis, disease of the brain or its meninges, or of the- spinal cord; certain fevers; poisoning by lead, alcohol, or tobacco, etc. See Amaurosis; Am- blyopia; Asthenopia; Hemeralopia; Nycta- lopia; Eye, Diseases of the; and Colob- Bt.IXDNESS. BLIND PREACHER, The. The Rev. Wil- liam Henry Milburn, for many years the Chap- lain of the United States Senate. BLIND SHELL. See Projectile. BLIND SPOT. A roundish oval spot in each retina, which is blind. It corresponds to the place of entry of the optic nerve. The spot is. some 1.8 millimeters in width, i.e. sul)tends an angle of some 6° (the limits given bv Helmholtz are 18° 55' and W 25'). That i't is totally blind, whether to brightness or color, was first proved by the French physicist Mariotte in 1008, and is easily demonstrable. Its form differs somewhat in different eyes. With careful obser- vation, it can be shown to possess certain irregu- lar prolongations, which represent the course of the large blood-vessels that enter the eye along with the nerve. A striking experiment may be performed as follows: Close or liandage the right eye. and with the left gaze steadily at a point upon a a Blind Spot ok Lkft Eye (plane-projection). Reiluowl from a lur^ts diagram, in which the distance from the inner edite of the point of n.^ation a. to the Inner edtre of the blind spot was 54.6 cm. The distance <it the point of tt.Ta- tion from the eye in the experiment wa» 2.2 m. wall or screen some 7 feet distant. Let another person seat himself directly before the wall, on your left-hand side, in such a position that his forehead is on a level with the point of gaze, and his nearer cheek some 50 centimeters distant.
