DOLLOND -DOLPHIN. 



705 



DOLLOND, PETER, eldest son of the preceding, 

 was born in 1730. In 1765, he communicated a 

 paper to the royal society, upon his improvement of 

 telescopes, and another in 1772, on his additions to, 

 and alterations of, Hadley's quadrant. He also gave 

 a description of his equatorial instrument for cor- 

 recting the errors arising in altitude from refraction. 

 In 1789, he published Some Account of the Disco- 

 very made by his Father in refracting Telescopes. 

 He died in 1820. 



DOLOMIEU, DEODAT GUY SILVAIN TANCREDE 

 GRATET PE, a geologist and mineralogist, was born, 

 June 24, 1750, at Dolomieu, in Dauphiny, and was 

 received into the order of the knights of Malta while 

 yet a child. On his first cruise in the Mediterranean, 

 he killed one of the officers of his galley in a quarrel. 

 He was tried at Malta, and condemned to lose the 

 robe of (the order ; but the grand master, considering 

 his great youth, reprieved him ; and the pope was 

 at last prevailed on to give his consent to a full par- 

 don. Dolomieu was in prison nine months, and, 

 during his confinement, acquired a taste for poetry. 

 He continued his studies at Metz, whither he was 

 transferred as an officer of a regiment of carabineers, 

 in garrison at that place. The duke de la Roche- 

 foucault became acquainted with him there, and, 

 through his -influence, Dolomieu was made a corres- 

 ponding member of the academy of sciences. In 

 order to devote himself entirely to his studies, Dolo- 

 mieu left the military service, and returned to Malta, 

 whence he went to Portugal, in 1777, in the retinue 

 of the bailli de Rohan. He examined that country, 

 visited Sicily and the neighbouring islands, Naples, 

 and mount Vesuvius, in 1781, travelled over the 

 Pyrenees in 1782, and in 1783 passed through Cala- 

 bria, which had just been desolated by an earth- 

 quake. In consequence of some secret communica- 

 tions, which he made to the grand master on his 

 return, being betrayed to the court of Naples, which 

 was interested in them, he was forbidden to enter 

 that kingdom, and experienced many difficulties in 

 Malta. Leaving this island again, he visited the 

 mountains of Italy, the Tyrol, and the country of the 

 Grisons. He returned once more to Malta, for the 

 purpose of bringing off his collection, and thence 

 went to France, in May, 1791, where he resided at 

 Roche-Guyon, the estate of his friend the duke de 

 la Rochefoucault, who had fallen a victim to the 

 revolutionary fury. 



After the ninth Thermidor, he renewed his geologi- 

 cal excursions through France, always on foot, with 

 a hammer in his hand, and a bag on his back. In 

 1796, he was appointed engineer and professor, and, 

 at the establishment of the institute, was made a 

 member of that society. In these capacities, he pub- 

 lished several works relative to the theory of the 

 earth and the nature of minerals. He eagerly seized 

 the opportunity of visiting Egypt, offered to him by 

 the French expedition to that country. But the oc- 

 cupation of Malta on the way made him dissatisfied 

 with the whole undertaking, and the situation of the 

 army in Egypt soon condemned him to inactivity. 

 In March, 1799, he embarked for Europe. On the 

 passage, the vessel sprang a leak, and only succeeded, 

 after great efforts, in reaching the harbour of Taren- 

 tum. There the crew were treated as prisoners of 

 war; and, when the rest were set at liberty, Dolo- 

 mieu was recognised and detained as a prisoner. 

 During twenty-one months, he suffered hardships and 

 privations of every kind. Even books and writing 

 materials were denied him. His firmness, however, 

 sustained him. On the margins of two or three books, 

 which he had contrived to conceal from the eyes of 

 his sentinel, he wrote his treatise on mineralogical 

 philosophy: his pen was a piece of wood, and the soot 



of his lamp supplied him with ink. In consequence 

 of the peace concluded between France and Naples, 

 March 15, 1801, he obtained his liberty, and receiv- 

 ed the professorship of mineralogy in the museum of 

 natural history, which had become vacant by the 

 death of Daubenton. His health, however, having 

 been already undermined by his captivity, was en- 

 tirely destroyed by a journey to Switzerland, Savoy, 

 and Dauphiny, in 1801, and lie died at Chateauneuf, 

 Nov. 28 of the same year. With a passionate love 

 for geology, Dolomieu united all the qualities, physi- 

 cal and moral, necessary for the successful study of 

 this science; and it is therefore much to be regretted, 

 that he was prevented from combining and systema- 

 tizing his views and observations. 



DOLOMITE ; a mineral species, specimens of 

 which occur under considerably diversified aspects. A 

 variety called bitter spar, and sometimes rhomb spar, 

 is found in crystals, having the form of a rhomboid, 

 with angles varying from 106 15' to 107 20' and 

 from 73 45' to 72 40'. It cleaves with ease parallel 

 to this form. Colour grayish, yellowish or reddish 

 brown; hardness a little above that of calcareous 

 spar, but is easily scratched with the knife; semi- 

 transparent and very brittle. It is found in steatite 

 or soapstone, disseminated in crystals, varying in 

 size, from three-fourths to one-fourth of an inch in 

 diameter. A second variety of this species is deno- 

 minated pearl spar. It differs from bitter spar chiefly 

 in the slightly curvilinear faces of its crystals, and in 

 possessing a more shining, pearly lustre, and usually 

 lighter shades" of colour, being sometimes quite white. 

 It is found principally in metallic veins accompany- 

 ing the ores of lead and tin. The most abundant 

 variety of the present species goes by the name of 

 dolomite. It is massive, or consists of fine crystalline 

 grains, but slightly coherent, and of various shades 

 of white. It constitutes beds of very great extent, 

 and therefore belongs to the class of rocks; and, as 

 such, comes under the division of primitive rocks. 

 It abounds in the Apennines, the Tyrol, Switzer- 

 land, and Tuscany. It is frequently employed as a 

 marble, both in Europe and America. It is com- 

 posed of carbonate of lime and carbonate of magne- 

 sia; but the relative quantity of the two seems not to 

 be exactly the same in all varieties. Its decomposi- 

 tion is conceived to form a good soil for agriculture. . 



DOLPHIN (delphinus). A cetaceous animal, the 

 name of which is improperly applied to a fish, the 

 coryphcena hippuris, or dolphin of navigators, so 

 celebrated for the beautiful changes of colour which 

 it exhibits when dying. The real dolphin has been 

 rendered famous by the tales related of it by the an- 

 cient writers; one of the most familiar of which is 

 the fable of the musician Arion. There are several 

 species of dolphins enumerated by naturalists. Those 

 which occur commonly are D. delphis, or common 

 dolphin., D. rostratus, and D. tursio. Dolphins are 

 cosmopolite animals, inhabiting every sea, from the 

 equator to the poles, enduring equally well the ex- 

 tremes of heat or cold; they are gregarious, and 

 swim with extraordinary velocity, outstripping in 

 their course the fleetest vessels. During the electri- 

 cal excitement of the atmosphere previous to changes 

 of weather, they are observed to be very active and 

 vivacious, leaping considerable distances out of the 

 water, and displaying, in their rapid movements, 

 their uncommon muscular powers. The characters 

 distinctive of the common dolphin are black, be- 

 neath white; snout porrect, depressed; jaws with 

 forty or forty-two curved, pointed teeth on each side; 

 length eight or ten feet; flesh coarse, rank, and dis- 

 agreeable (used by the Laplanders, and the inhabi- 

 tants of Greenland, as food, but is apt to produce sick- 

 ness in persons who eat it for the first time); skin 

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