DOLLOND. 365 DOLOMIEtr. his eldest son, Peter, to an optician; and after the latter had established himself in business on his own aeeount, he was joined by his father in 1752. John Uollond now devoted himself to the improvement of the refracting telescope, in which work he was encourajied by the most distinguished seieutilic men of the time. After a series of well-contrived experiments and re- searches, commenced in 1757 and carried on for several years, he succeeded in conslrucling lenses where a concave lens of Hint glass was combined with a coinex lens of crown glass with the re- sult that images were produced without any colored border. (See Achromatism.) This was undoubtedly the greatest improvement that the telescope had received since its first invention. The memoir (published in the Philosophical Trnnsdctioiis for 1758) in which he gave an ac- count of his investigations, was rewarded by the council of the Ttoyal Society with the Copley medal. In 1701 Dollond was appointed optician to the King, and was elected a fellow of the Royal Society. His two sons continued to carry on the business with great success. Consult Kelly, l.ifc of ■foliii Dotlond (London, 1808). DOLL'S HOUSE, A. The English version of Et Duhkchjciii. a play by Henrik Ibsen (q.v.), produced in Christiania in 1S7!) and in London in 1SS9. The theme is the right of individualism in woman, which is set forth in the disillusioning experience of Nora Helmer. the young wife of a man fettered by conventional idealism. DOLLY VARDEN. In Dickens's Barimbjj Riidgc, the coquettish daughter of Gabriel Var- den, a locksmith, whom she rules completely. She is impulsi-e, soft-hearted, and full of pretty strategies. Her dainty dress of flowered dimity, cut short enough to show her neat ankles and buckled shoes, gave the name Dolltj Varden to a, style of dress which can;e into fashion soon after Bnrnahy Rudge was published. DOLLY VARDEN TROUT (from the color, which resembles a Dulh/ 'arden, a gown of gay muslin print worn by women about 1805-70). The common brook-trout {Salvcliniis malma). a char of the mountains "f western Xorth Amer- ica, "from the upper Sacramento to Montana, Alaska, and Kamchatka." It has a stout body, large head and mouth, and the back more ele- vated and less compressed than the Eastern brook- trout (Salceli)nis fotitinnlis) ; the tail is almost truncate, and the adipose fin is unusually large. "General color, olivaceous; the sides with round red spots nearly the size of the eye, the back commonly with smaller pale ones, a feature of coloration which distinguishes this species at once from the others." It abounds in the streams of the northern Rooky Mountains, where it is also known as bull-trout or red-spotted trout ; and in the far Xorthwest, where it has the Kamehatkan name 'malma;' it descends to the sea and some- times reaches a weight of twelve pounds. It is one of the most heautiftil and active of the Salmonidie. and has been extensively trans- planted tn waters in the northeastern United States and Europe. See Trout. DOLMEN fBret.. table-sfone. from dol. table + vien, Welsh tvnen. stone; the Vel!«h equivalent is crnmlrrh, bending slab). The name given to a class of monuments of prehistoric civilization, consisting of several great stone slabs, set edgewise in the earth and supporting a flat capstone for the roof, designed for a se- pulchral chamber. The greatest historic in- terest attaches to these monuments, for several reasons. They were erected in the British Isles, in northwestern France, in Spain, along North- ern Africa, in Syria, and chambered mounds exist as far east as Japan. They mark the Neolithic period in Europe, and their erection may be called the beginning of engineering. In (iuern- .-.cy and elsewliere they are styled Druid altars, and are associated with Druidical rites. By some they have been attributed to tlu" Celts, and this raises the question whether all the dolmen- builders of Northern Africa and Europe and even in Japan were of the same race. If they were, they would belong rather to the Iberic branch of Sergi's Eurafrie species, a strain of whose blood may have reached the Orient. Dol- mens were sometimes covered with innnense tu- nuili, and again the earth envelope reached only the capstone. Some of the mounds were of great size, as that of Silbury Hill, Wiltshire, 170 feet high, and 310 feet along the slope. In some of the chambers might have been single interments; in others, says Keane, the same mound had to do duty for many generations, the original cell expanded into the 'family vault.' developing a system of lateral chambers 30 X 10. and 8 feet high, with roof slabs of corresponding size, some weighing 10, 20, and even 40 tons. Consult: Keane, Ethnolo(jy (Cambridge. 1896) ; Borlase, The Dolmcnfi of Ireland (London, 1897). DOLOMIEU, do'lo'mye', Deodat Guy Silvain TANCKtDE Gratet de (1750-1801). A French geologist and mineralogist. He was one of the Knights of Malta when a boy, and fought a duel with and killed a brother knight, for which he was condemned to death, but was saved in consideration of his youth. He then turned his attention to science, and visited Portugal, Spain, and Sicily, making interesting observa- tions on the geological structure of the Pyrenees. He minutely described the earthquake in Cala- bria in 1783. and in later years studied the Alps, where he discovered the mineral 'dolomite,' which is named after him. He became ju'cifessor in the Paris School of Klines and a member of the Institute from its formation. In 1798 he was on the scientific stafT of Bonaparte's expe- dition to EgA'pt. Here he lost his health, and on the way home was left at Messina, where he was an object of political hatred because he had revealed in 1783 to the Grand Master of Malta the designs of the Nea])olitans against that island. lie was confined in a wretched dun- geon, clothed in rags, and given only a bed of straw. There he was kept twenty-one months. Denied writing materials, he made a pen from a piece of wood, and with the smoke of his lamp for ink, wrote on the margins of his Bible his Traits de philosophie miniralogique, and M6- moire sur I'espece minirale. At the conclusion of the treaty betw^een France and Naples, he was released and took the chair of mineralogy at the Museum of Natural History in Paris. His collections of mineralogy included numerous and valuable specimens. Besides the worl<s men- tioned above, he wrote: Voi/iifir aiix llc.i dr Lipari (1783); M^moire xiir le trcmblement de terre de la Calnbra (1783); }f^moire.i sur les ilvs Ponces (1788), etc. hac^pide's ' Eloge historique
