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 capacity of playwright. He married an actress, and the two spent three years in St Petersburg, where they were well received. In 1782 he produced at the Comédie Italienne an adaptation of Fielding’s novel with the title Tom Jones à Londres. His first great success was achieved with L’Épreuve villageoise (1785) to the music of Grétry. La Femme jalouse, a five-act comedy in verse (1785), Joconde (1790) for the music of Louis Jaden, Les Époux divorcés (1799), a comedy, and other pieces followed. Desforges was one of the first to avail himself of the new facilities afforded under the Revolution for divorce and re-marriage. The curious record of his own early indiscretions in Le Poète, ou mémoires d’un homme de lettres écrits par lui-même (4 vols., 1798) is said to have been undertaken at the request of Madame Desforges. He died in Paris on the 13th of August 1806.

 DESGARCINS, MAGDELEINE MARIE [] (1769–1797), French actress, was born at Mont Dauphin (Hautes Alpes). In her short career she became one of the greatest of French tragédiennes, the associate of Talma, with whom she nearly always played. Her début at the Comédie Française occurred on the 24th of May 1788, in Bajazet, with such success that she was at once made sociétaire. She was one of the actresses who left the Comédie Française in 1791 for the house in the rue Richelieu, soon to become the Théâtre de la République, and there her triumphs were no less—in King Lear, Othello, La Harpe’s Mélanie et Virginie, &c. Her health, however, failed, and she died insane, in Paris, on the 27th of October 1797.

 DESHAYES, GÉRARD PAUL (1795–1875), French geologist and conchologist, was born at Nancy on the 13th of May 1797, his father at that time being professor of experimental physics in the École Centrale of the department of la Meurthe. He studied medicine at Strassburg, and afterwards took the degree of bachelier ès lettres in Paris in 1821; but he abandoned the medical profession in order to devote himself to natural history. For some time he gave private lessons on geology, and subsequently became professor of natural history in the Muséum d’Histoire Naturelle. He was distinguished for his researches on the fossil mollusca of the Paris Basin and of other Tertiary areas. His studies on the relations of the fossil to the recent species led him as early as 1829 to conclusions somewhat similar to those arrived at by Lyell, to whom Deshayes rendered much assistance in connexion with the classification of the Tertiary system into Eocene, Miocene and Pliocene. He was one of the founders of the Société Géologique de France. In 1839 he began the publication of his Traité élémentaire de conchyliologie, the last part of which was not issued until 1858. In the same year (1839) he went to Algeria for the French Government, and spent three years in explorations in that country. His principal work, which resulted from the collections he made, Mollusques de l’Algérie, was issued (incomplete) in 1848. In 1870 the Wollaston medal of the Geological Society of London was awarded to him. He died at Boran on the 9th of June 1875. His publications included Description des coquilles fossiles des environs de Paris (2 vols. and atlas, 1824–1837); Description des animaux sans vertèbres découverts dans le bassin de Paris (3 vols. and atlas, 1856–1866); Catalogue des mollusques de l’île la Réunion (1863).

 DESHOULIÈRES, ANTOINETTE DU LIGIER DE LA GARDE (1638–1694), French poet, was born in Paris on the 1st of January 1638. She was the daughter of Melchior du Ligier, sieur de la Garde, maître d’hôtel to the queens Marie de’ Medici and Anne of Austria. She received a careful and very complete education, acquiring a knowledge of Latin, Spanish and Italian, and studying prosody under the direction of the poet Jean Hesnault. At the age of thirteen she married Guillaume de Boisguerin, seigneur Deshoulières, who followed the prince of Condé as lieutenant-colonel of one of his regiments to Flanders about a year after the marriage. Madame Deshoulières returned for a time to the house of her parents, where she gave herself to writing poetry and studying the philosophy of Gassendi. She rejoined her husband at Rocroi, near Brussels, where, being distinguished for her personal beauty, she became the object of embarrassing attentions on the part of the prince of Condé. Having made herself obnoxious to the government by her urgent demand for the arrears of her husband’s pay, she was imprisoned in the château of Wilworden. After a few months she was freed by her husband, who attacked the château at the head of a small band of soldiers. An amnesty having been proclaimed, they returned to France, where Madame Deshoulières soon became a conspicuous personage at the court of Louis XIV. and in literary society. She won the friendship and admiration of the most eminent literary men of the age—some of her more zealous flatterers even going so far as to style her the tenth muse and the French Calliope. Her poems were very numerous, and included specimens of nearly all the minor forms, odes, eclogues, idylls, elegies, chansons, ballads, madrigals, &c. Of these the idylls alone, and only some of them, have stood the test of time, the others being entirely forgotten. She wrote several dramatic works, the best of which do not rise to mediocrity. Her friendship for Corneille made her take sides for the Phèdre of Pradon against that of Racine. Voltaire pronounced her the best of women French poets; and her reputation with her contemporaries is indicated by her election as a member of the Academy of the Ricovrati of Padua and of the Academy of Arles. In 1688 a pension of 2000 livres was bestowed upon her by the king, and she was thus relieved from the poverty in which she had long lived. She died in Paris on the 17th February 1694. Complete editions of her works were published at Paris in 1695, 1747, &c. These include a few poems by her daughter, Antoine Thérèse Deshoulières (1656–1718), who inherited her talent.

 DESICCATION (from the Lat. desiccare, to dry up), the operation of drying or removing water from a substance. It is of particular importance in practical chemistry. If a substance admits of being heated to say 100°, the drying may be effected by means of an air-bath, which is simply an oven heated by gas or by steam. Otherwise a desiccator must be employed; this is essentially a closed vessel in which a hygroscopic substance is placed together with the substance to be dried. The process may be accelerated by exhausting the desiccator; this so-called vacuum desiccation is especially suitable for the concentration of aqueous solutions of readily decomposable substances. Of the hygroscopic substances in common use, phosphoric anhydride, concentrated sulphuric acid, and dry potassium hydrate are almost equal in power; sodium hydrate and calcium chloride are not much behind.

Two common types of desiccator are in use. In one the absorbent is placed at the bottom, and the substance to be dried above. Hempel pointed out that the efficiency would be increased by inverting this arrangement, since water vapour is lighter than air and consequently rises. Liquids are dried either by means of the desiccator, or, as is more usual, by shaking with a substance which removes the water. Fused calcium chloride is the commonest absorbent; but it must not be used with alcohols and several other compounds, since it forms compounds with these substances. Quicklime, barium oxide, and dehydrated copper sulphate are especially applicable to alcohol and ether; the last traces of water may be removed by adding metallic sodium and distilling. Gases are dried by leading them through towers or tubes containing an appropriate drying material. The experiments of H. B. Baker on the influence of moisture on chemical combination have shown the difficulty of removing the last traces of water.

In chemical technology, apparatus on the principle of the laboratory air-bath are mainly used. Crystals and precipitates, deprived of as much water as possible by centrifugal machines or filter-presses, are transported by means of a belt, screw, or other form of conveyer, on to trays staged in brick chambers heated directly by flue gases or steam pipes; the latter are easily controlled, and if the steam be superheated a temperature of 300° and over may be maintained. In some cases the material traverses the chamber from the coolest to the hottest part on a conveyer or in wagons. Rotating cylinders are also used; the material to be dried being placed inside, and the cylinder heated by a steam jacket or otherwise.

 DESIDERIO DA SETTIGNANO (1428–1464), Italian sculptor, was born at Settignano, a village on the southern slope of the hill