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 veins in the leg from the wearing of a tight garter, and of piles as the result of the pressure of an ovarian tumour or a pregnant uterus, or of disease of the liver.

Sometimes the trouble is begun by a direct injury to the vein, which, by setting up an inflammation, weakens the coats of the vein, which then yield under the pressure of the blood-stream. In the case of varicocele, the dilatation of the veins is probably of developmental origin; many other causes are given, but not one of them appears satisfactory. Examination of a varicose vein shows that it is increased in length as well as in capacity. In some parts of its course the vein has its coats much thickened, but at those places where there is dilatation the walls are very thin. Veins thus affected give rise to pains and achings, and they are, moreover, liable to attacks of inflammation which end in clotting of the blood (thrombosis). This is a dangerous condition, as a sudden or violent movement is apt to cause the detachment of a piece of the clot, which, carried up to the brain or the lung, may cause sudden death. Less serious results of varicose veins are swelling of the parts below (oedema), ulceration and abscess.

VARIOLITES (Lat. variola, smallpox), in petrology, a group of dark green basic igneous rocks which, especially on weathered surfaces, exhibit pale coloured spots that give them a pockmarked appearance. In some conditions these spots weather out prominently; they are grey, pale green, violet or yellowish, while the matrix of the rock is usually dark green. The variolites are related most closely to the basalts or diabases. They are nearly always much decomposed, and, since they are also fine-grained rocks, their original composition may be much obscured by secondary changes. The variolitic spots are rounded in outline and are often about a quarter of an inch in diameter, but may much exceed this size. They have a radiate structure and are sometimes, though not generally, zoned with concentric circles, of different appearance and composition. Many authors have compared them with the spherulites of the acid rocks (obsidians and rhyolites), and undoubtedly some kinds of variolite are merely glassy spherulitic varieties of basalt. The tachylyte selvages of the dolerite dikes of the west of Scotland, for example, often contain large brown spherulites which are easily visible in hand specimens. These spherulites consist of very thin divergent fibres, and their nature is often difficult to determine on account of the indefiniteness of the optical characters of minerals in this state. It seems probable, however, that they are mostly felspar embedded in dark brown glass. Small phenocrysts or skeleton crystals of olivine, augite and plagioclase felspar may occur in these tachylytes.

 VARISCITE, a native hydrous aluminium phosphate, AlPO4·2H2O named by A. Breithaupt, in 1837, in consequence of its occurrence in the Saxon Voigtland (Variscia). It is a green mineral generally occurring as an incrustation or in nodules. A compact nodular variety was discovered about 1894 in Cedar Valley, near Old Camp Floyd, Utah, and was described by Dr G. F. Kunz as utahlite. Its beautiful apple-green colour has led to its use, when cut and polished, as an ornamental stone. The term utahlite must be distinguished from utahite, the name given by A. Arzruni to a basic ferric sulphate, 3(FeO)2SO4·4H2O, from Utah.

 VARLEY, CORNELIUS (1781–1873), English water-colour painter, a younger brother of (q.v.), was born at Hackney, London, on the 21st of November 1781. He was educated by his uncle, a philosophical instrument maker, and under him acquired a knowledge of the natural sciences; but about 1800 he joined his brother in a tour through Wales, and began the study of art. He was soon engaged in teaching drawing. From 1803 till 1859 he was an occasional exhibitor in the Royal Academy; and he also contributed regularly to the displays of the Water-Colour Society, of which, in 1803, he was one of the founders, and of which he continued a member till 1821. His works consist mainly of carefully finished classical subjects, with architecture and figures. He published a series of etchings of “Boats and other Craft on the River Thames,” and during his life as an artist he continued deeply interested in scientific pursuits. For his improvements in the camera lucida, the camera obscura and the microscope he received the Isis gold medal of the Society of Arts; and at the International