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 invented in 1914 by Dr. E. E. Fournier d’Albe, then a lecturer in physics in the university of Birmingham. It is based upon the properties of selenium, an element which is a better electrical conductor in light than in darkness. A beam of light is rendered intermittent by the interposition of a revolving siren disc and is then concentrated into a small bright point on the paper to be read. If the point on the paper is white, it will reflect the light; if it is black it will not. A selenium cell placed close to the paper, on receiving the reflected beam of intermittent light, will respond to each flash by a change in conductivity, and if the frequency of the flashes is of the “musical” order (between 30 and 30,000 flashes per second), a telephone receiver connected with the selenium and a battery will sound a musical note. A blind person could thus tell whether the paper is black or white.

That is the principle of the optophone. In practice a small row of luminous points is substituted for a single point, and each point in the row is given a different frequency by suitably perforating the siren disc. The row, usually of five or six points, just fills up the size of the tall letters of the print to be read. When the whole row falls upon the black stem of a letter there is silence in the telephone. As the letters pass their various shapes are indicated by the sounding or silence of the different notes, and after some practice the blind person learns to recognize letters from their sounds, and so to read ordinary type.

The first reading test was given by the inventor in March 1917, the matter read being a leading article in The Times. In Aug. 1918, Miss Mary Jameson, a blind pupil from Norwood, gave the first public reading demonstrations, reading an unknown page from a book at a speed of about two words per minute. Later, with an improved instrument, she attained a speed of about 20 words per minute. A new type of optophone was brought out in 1920 by Barr & Stroud, of Glasgow. In this instrument two selenium cells were used, balanced against each other in such a manner that white paper produced silence, and the black letters themselves made the musical sounds. Reading demonstrations were also given with this instrument, but any advantage in the way of ease of reading was found to be counter-balanced by a greater delicacy and complexity of adjustment. The new type is known as the “black-sounder,” and the original type is termed the “white-sounder.” The latter type was approved by the Inventions and Research Committee of the National Institute for the Blind in 1921 after an exhaustive series of tests. The optophone is intended to place the world’s printed literature once more within reach of the blind. It is applicable, without special preparation, to any language, and can also be used for reading typescript, but not handwriting.

 ORANGE FREE STATE (see 20.151), a province of the Union of S. Africa. At the 1911 census it had a pop. of 528,174 compared with 387,315 in 1904—an increase of 26.67%. Whites numbered 175,189, coloured 352,985. In 1918 the white pop. was 181,678. The increase in pop. since 1904 was very largely due to the development of agriculture and stock farming, the province being essentially a pastoral region.

The only big town is the capital, Bloemfontein (pop. in 1911 26,925). While new settlers included many of British origin, the white inhabitants remained predominantly of Dutch descent. Nearly all the coloured people are Bantu and in 1911 the province had only 108 Asiatics. A higher proportion, 50.77 %, of the natives professed Christianity than in any other province of the Union.

There were in 1918 only 5,588 persons (all races and both sexes) engaged in factories in the province, but in Jagersfontein it possesses one of the chief diamond mines in S. Africa, and there is a group of small but rich diamond mines in the Boshof area, proclaimed in 1906, 1910 and 1912. There are coal mines by the Vaal at Vereeniging, which produced 469,000 tons in 1910 and 838,000 tons in 1919.

Dr. A. E. W. Ramsbottom was the first administrator, being succeeded by Mr. H. C. Wessels. Both had been members of the Ministry during the brief period (July 1907–May 1910) while the province had been a self-governing colony. The provincial administration at first continued the system of compulsory bilingual education enforced in 1908, but the struggle conducted by the English-speaking part of the people over the medium of instruction came virtually to an end in 1912, the provincial council having adopted, in the main though still with a bias in favour of the Dutch language, the proposal suggested by the Union Parliament that up to standard IV. instruction in the schools should be given in the “home language” of the scholar. In 1920 an ordinance was passed recognizing “Afrikaans,” i.e. the Taal or colloquial Dutch, as equivalent to Netherlands Dutch as a medium of instruction, and its adoption, for Dutch scholars, was very general. In most respects the provincial administration was progressive and was conducted on non-party lines. (For the administrative system see .) Provincial expenditure rose from £511,000 in 1912–3 to £611,000 in 1917–8, the amount spent on education in the years named being £250,000 and £473,000 respectively.

The province was the stronghold of the Dutch Nationalists. Up to his death in 1916 ex-President Steyn, who lived near Bloemfontein, though he held no office, exercised very great influence on public affairs. In the crisis caused by the World War Steyn opposed operations against German S.W. Africa. There followed the rebellion of Gen. De Wet, the Free State being the principal theatre of the campaign. Gen. Hertzog, the parliamentary chief of the Dutch Nationalists and after Steyn’s death their undisputed leader, carried the Free State in the elections of 1915, 1920 and 1921. In Feb. of the last-named year, when he had declared for the secession of the union from the British Empire, his party won 16 out of the 17 constituencies into which the province was divided (see ).

 ORDNANCE (see 20.189.)—. The principal requirements from a gun are accuracy, high muzzle velocity and high remaining velocity at any given range. These points are dependent on the ballistics, or power, of the gun, on the twist and form of the rifling, and on other factors outside the gun, such as the weight and shape of the projectile and the design of the driving-band on the projectile.

At the same time as definite conditions are laid down for these main requirements, certain limitations are imposed upon the designer in connexion with the working pressures in the gun, the length and weight of the gun, the feasibility of repair, and the length and weight of the projectile. These various factors must be considered from the point of view of their relation to each other as they are to a very large extent interdependent, and variation in any one of them will react on one or more of the others. The limiting factor in the working pressure is the strength of the gun to resist the firing stresses, and any increase in these beyond a certain limit will necessitate a corresponding increase in the strength of the gun, that is, in the amount of material employed in its construction, which obviously entails an increase in the weight of the gun, a very important consideration. The length of the gun has an important effect on ballistics, and any increase in this respect not only is accompanied by increased weight but also affects the question of the space occupied, another important consideration. Further, any variation in the weight or length, or both, of the gun will affect the position of the centre of gravity, and so affect the design of the mounting or carriage. Another aspect of the question of length is its effect upon the “girder strength” of the gun. In modern ordnance efforts are made to place the centre of gravity as near the breech as possible, and, the gun being supported on its mounting at or near this point, with long guns a considerable proportion of the total length remains unsupported, and therefore has a tendency to “sag” due to its own weight. Theoretically a longer gun gives better ballistics, but in practice the length of modern guns is usually 45 to 50 calibres; though this has been sometimes exceeded in what may be termed “freak” guns, and may in future be exceeded in hyper-velocity