GLA.TZ GLEICHEN. 



479 



ffight glass is a telescope made for viewing objects 

 ai night. 



Half- hour glass, frequently called watch glass, is 

 used at sea to measure the time which each watch 

 lias to stay upon deck, '\\tfiog or sweat the glass, 

 is to turn it before the sand has quite run out, and 

 thereby gaining a few minutes each half hour, to 

 muke the watch too short. Glass is used in the plu- 

 ral to denote the duration of a naval action ; as, 

 ' ' They fought yard-arm and yard-arm three glasses," 

 that is, an hour and a half. 



GLATZ ; acountyand circle in the Prussian govern- 

 ment of Breslau, surrounded by high mountains. 

 The soil is fertile, and the air salubrious, and there 

 are several mineral springs at Cudowa, Neurode, and 

 Reinertz ; 360 square miles, with 61,400 inhabitants. 

 The See/elder (lake fields), which are always under 

 water, which never freezes, and never increases nor 

 diminishes, are 2000 feet high. The capital of the 

 county is \ 



Glatz, an important fortress, which was besieged 

 in 1742, 1759, and 1807. To the former county of 

 Giatz belonged also the circle of Habelschwerdt, 297 

 square miles, with 39,000 inhabitants, in which are 

 Liindeck, containing warm baths, and Niederlange- 

 nau, containing acidulous springs. Pop. above 8000. 

 GLAUBER, JOHN RODOLPH, a physician of Am- 

 sterdam, who died in 1668, at a very advanced age. 

 lie has rendered important services in chemistry, 

 notwithstanding his dreams of the transmutation of 

 metals. Chemistry is indebted to him tor an im- 

 proved construction of furnaces, for facilitating many 

 chemical processes, for the mode of preparing the 

 fuming nitric acid by means of sulphuric acid, and 

 for the salt (the sulphate of soda), which has been 

 named from him, and which he discovered acciden- 

 tally in common salt, as he was obtaining from it 

 the fuming muriatic acid, by distillation with sul- 

 phuric acid. Astonished at finding a crystallized 

 salt among the residuum, possessing medicinal pro- 

 perties, he named it sal mirabile (the wonderful salt). 

 It is used as a purgative ; is here and there found 

 in a natural state, but is chiefly prepared by art, and 

 is a neutral salt, containing water 56 parts, sul- 

 phuric acid 24-64. and soda 19-36. Its crystals are 

 large, six-sided prisms, and it has a bitter, cooling 

 taste. In a dry air, it falls into a white powder, and 

 loses 56 parts in the 100 of its weight, but still re- 

 tains its purgative properties, which are even increas- 

 ed in the part which remains. Nearly all the Glau- 

 ber's salt consumed in America is prepared from the 

 sea water, and principally at the large salt-works of 

 Massachusetts. This salt is obtained only in the 

 winter, and seems not to exist in solution in the sea- 

 water, but to be formed by the mutual decomposi- 

 tion of the solutions of sulphate of magnesia and 

 chloride of sodium at a freezing temperature. In 

 fact, during the extreme cold weather, a crystalline 

 deposit, consisting chiefly of sulphate of soda, is 

 formed in the pickle vats, whilst, at temperatures 

 above freezing, no other salts are obtained from the 

 same menstruum, except muriate of soda, sulphate 

 of magnesia, hydrochl orates of magnesia and lime, 

 &c. ; but no sulphate of soda. That crystalline de- 

 posit is taken out with iron rakes, having strainers 

 attached to them, and is purified, for sale, by crystal- 

 lization ; the best formed crystals are sometimes dried 

 and sold in their impure state. 



GLAUCUS ; a fisherman of Anthedon.in Bceotia, 

 who was received among the national deities 01 

 Greece, not long before the time of ^Eschylus, am; 

 to whom, as a god of the sea, the power of prophesy 

 was attributed. Apollonius makes him render oracles 

 to the Argonauts, on the coast of Mysia. (See Ovid, 

 Metamorph., xiii. 90C.) 



GLAZING. To prevent the penetration of fluids, 

 it is necessary that earthen vessels should be glazed, 

 or covered with a vitreous coating. The materials 

 of common glass would afford the most perfect glaz- 

 ing to crockery ware, were it not that the ratio of its 

 expansion and contraction is not the same with that 

 of the clay ; so that a glazing of this sort is liable to 

 cracks and fissures, when exposed to changes of tem- 

 perature. A mixture of equal parts of oxide of lend 

 and ground flints is found to be a durable glaze for 

 the common cream-coloured ware, and is generally 

 used for that purpose. These materials are first 

 ground to an extremely fine powder, and mixed with 

 water to form a thin liquid. The ware is dipped into 

 this fluid and drawn out. The moisture is soon ab- 

 sorbed by the clay, leaving the glazing particles upon 

 the surface. These are afterwards melted by the 

 heat of the kiln, and constitute a uniform and durable 

 vitreous coating. The English and French manu- 

 facturers find it necessary to harden their vessels by 

 heat, or bring them to the state of biscuit, before 

 they are glazed ; but the composition used by the 

 Chinese resists water, after it has been once dried in 

 the air, so as to bear dipping in the glazing liquid 

 without injury. This gives them a great advantage 

 in the economy of fuel. 



Painters call glazing the laying a transparent co- 

 lour over one of a different tint. 



GLEDITSCH, JOHN THEOPHILUS, professor of 

 natural history and botany, and member of the 

 academy of sciences at Berlin, was born at Leipsic, 

 February 5, 1714. He died at Berlin, October, 17SC, 

 where, after having lived and laboured in many other 

 places, he was superintendent of the botanic garden. 

 He was a very scientific botanist, and was the first to 

 produce a scientific arrangement of forest trees. 

 Several very esteemed works were first published 

 after his death, by his son-in-law Gerhard, at Berlin. 

 Among the best are his Catalogus Plantantm (of the 

 Ziethen garden at Trebnitz), his Consideratio Epi- 

 cnseos Siegesbekiance in Ltnncei Systema Plantarum, 

 etc. Lucubratiuncttla de Fuco subgloboso sessili et 

 rnolli in Murchia reperiundo, a German translation of 

 which may be found in his dissertations upon botany, 

 in 3 vols. ; his Systematic Introduction to the Know- 

 ledge of Forests (Systematische Einleituiig zum 

 Studium der Forstwissenschaff) ; his Practico-Theo- 

 retical History of Medical Plants (Theoretisch- 

 praktische Geschickte der Medicinalpflanzeri) ; his 

 Natural History of the most useful Domestic Plants 

 (Naturgeschichte der natzlichsten einheimischen 

 Gewachse) ; his Botanica Medica (published by I". 

 W. A. Luders, one of the most distinguished pupils) , 

 and his Remarks in Relation to Botany and Medicine 

 (Bemerkungen in Bezvg auf Botanik vnd Medicin). 

 His dissertations are to be found partly in the Me- 

 moirs of the Friends of Natural History, at Berlin, in 

 the Annals of the Berlin Academy, and in the Varie- 

 ties (Mannigfaltigkeiten) of Martini, as well as many 

 valuable botanic catalogues. He also published the, 

 second edition of the Philosophia Botanica of Lin- 

 naeus. The English naturalist Catesby has, in honour 

 of him, given the name Gledidia to an exotic plant. 



GLEE, in music; a vocal composition in three or 

 more parts, generally consisting of more than one 

 movement, the subject of which may be either gay, 

 tender or grave, bacchanalian, amatory or pathetic. 

 GLEICHEN, ERNEST, according to some, Louis, 

 count, sprang from a celebrated German family now 

 extinct, went on a crusade to Palestine, fought against 

 and was taken prisoner by the Turks. The follow- 

 ing story is related of him, for the truth of which we 

 will not vouch. One day, as the unfortunate man 

 was at work on the road, the sultan's daughter Faw 

 him, and, moved by pity and love, offered him his 



