Page:Encyclopædia Britannica, Ninth Edition, v. 14.djvu/194

 182 L A C L A C over and around the twig. From this living tomb the female insects, which form the great bulk of the whole, never escape. After their impregnation, which takes place on the liberation of the males, about three months from their first appearance, the females develop into a singularly amorphous-like organism consisting in its main features of a large smooth shining crimson -coloured sac the ovary with a beak stuck into the bark, and a few papillary processes projected above the resinous surface. The red fluid in the ovary is the substance which forms the lac dye of commerce, and, when the young are allowed to hatch out, the greater part of this colouring matter is lost, and only a dead resinous substance remains on the twig. To obtain the largest amount of both resin and dye-stuff therefore it is necessary to gather the twigs with their living inhabitants in or near June and November. Lac encrusting the twigs as gathered is known in commerce as &quot;stick lac &quot;; the resin crushed to small fragments and washed free from colouring matter constitutes &quot; seed lac &quot; ; when melted, strained through thick canvas, and spread out into thin layers, this is known as &quot; shell lac,&quot; and it is in this last form that the resin is usually brought to European markets. Shell lac, which varies in colour from a dark amber to an almost pure black appearance, may be bleached by dissolv ing in a boiling lye of caustic potash and passing chlorine through the solution till all the resin is precipitated. Bleached lac takes light delicate shades of colour, and dyed a golden yellow it is much used in the East Indies for working into chain ornaments for the head and for other personal adornments. Lac is a principal ingredient in sealing wax, and forms the basis of some of the most valuable varnishes, besides being useful in various cements, &c. (see LACQUER). Average stick lac contains about 68 per cent, of resin, 10 of lac dye, and 6 of a waxy substance. The resin of lac is a composite body, whose constituents behave differently in presence of chemical reagents. Lac dye, which is separated by washing stick lac in hot or cold water or in a weak alkaline solution, and dried either by exposure over a fire or in the sun, comes into commerce in the form of small square cakes. It is in many respects similar to, although not identical with, cochineal, and will dye less brilliant shades than that colour. It contains about 50 per cent, of colouring matter, with 25 per cent, of resin and 22 per cent, of earthy admixture, &c. It is used for dyeing silk and wool, for which purposes it is dissolved in dilute sulphuric acid or somewhat stronger hydrochloric acid ; and the substance to be dyed is prepared with a mordant of strong lac spirit, which consists of a solution of stannous chloride. Lac dye has been used from time immemorial in the East, but the knowledge of the substance in the West is comparatively recent. It was first brought to Europe by the East India Company as a substitute for cochineal. The best lac dye comes from Calcutta, Lac lake is an alumina lake con taining about 50 per cent, of colouring matter, 40 per cent, of resin, and 9 or 10 per cent, of alumina. LACAILLE, NICOLAS Louis BE (1713-1762), a zealous and successful astronomer, was born at Rumigny, near Rheims, March 15, 1713. Left destitute by the death of his father, who held a post in the household of the duchess of Vendome, his theological studies at the College de Lisieux in Paris were prosecuted at the expense of the duke of Bourbon. After he had taken deacon s orders, however, he devoted himself exclusively to science, and, through the patronage of Cassini, obtained employment, first in survey ing the coast from Nantes to Bayonne, then, in 1739, in remeasuring the French arc of the meridian. The success of this difficult operation, which occupied two years, ancl achieved the correction of the anomalous result obtained by the elder Cassini in 1684, was mainly due to Lacaille s industry and skill. He was rewarded by admission to the Academy, and the appointment of mathematical professor in Mazarin college, where he worked diligently for some years in a small observatory fitted up for his use. His desire to observe the southern heavens led him to propose, in 1750, an astronomical expedition to the Cape of Good Hope, which was officially sanctioned, and fortunately executed (see ASTRONOMY, vol. ii. p. 757). On his return in 1754 he was distressed to find himself an object of public attention, and withdrew to his former retreat in Mazarin college, where he died, March 21, 1762, of an attack of gout aggravated by unremitting toil. Lalande said of him that, during a comparatively short life, he had made more observations and calculations than all the astronomers of his time put together. And, his carefulness equalling his rapidity, the quality of his work rivalled its quantity. The rectitude of his moral character earned him universal respect, and his career ranks, if not amongst the most brilliant, amongst the most useful and honourable in the annals of science. His principal works are Astronomies Fundamcnta, 1757 ; Tabular Solarcs, 1758, giving, for the first time, corrections for planetary perturbations ; Ccelum australe stclliferum, 1763, a catalogue of 10,035 southern stars ; Observations sur 515 etoilcs du Zodiaque, 1763 ; Lemons elementaires de Mathematiques, 1741, frequently reprinted ; ditto de Mecaniquc, 1743, &c. ; ditto d Astronomic, 1746, 4th edition augmented by Lalande, 1779 ; ditto d Optiquc, 1750, &c. Calculations by him of eclipses for eighteen hundred years were inserted in L art do verifier Us dates, 1750 ; he communi cated to the Academy in 1755 a classed catalogue of forty-two southern nebulae, and gave in vol. ii. of his jp/iemeridcs, 1754, practical rules for the employment of the lunar method of longi tudes, proposing in his additions to Bouguer s TraiU de Naviga tion, 1760, the model of a nautical almanac. LA CALLE, or LA GALA, a seaport town of Algeria, in the province of Constantine, the centre of the Algerian and Tunisian coral fisheries. It lies .40 miles east of Bone and 10 miles from the Tunisian frontiers. The harbour is small and inconvenient, but it is proposed to construct a military port and harbour of refuge a little to the west. La Calle proper, or the old fortified town, is built on a ridge of rocks about 400 yards long, connected with the main land by a bank of sand ; but a new town has grown up along the coast. Besides the coral fisheries the curing of sardines is largely carried on. The population, without the garrison, was 3308 in 1871. La Calle is mentioned as Mersa el Kharez by El Belm (see Journ. Asiat., 1859), and was even then the residence of coral merchants. In the early part of the 18th century it was the seat of an English trading factory, but on the failure of the company the French- African Company moved their factory from Bastion de la France to La Calle. The company was suppressed in 1794. In 1806 Mr Blanckley, British consul-general at Algiers, obtained the right of occupying Bone and La Calle for an annual rent of 11,000 ; but though the money was paid for several years no practical effect was given to the agreement. The French regained possession in 1817, were expelled during the wars of 1827, but returned and rebuilt the place in 1836. See Abbe&quot; Poirefr, Voyage en Barbaric, Paris, 1787; Brougliton, Six Years in Algeria, anil Playfair, Travels in the Footsteps of Bruce. LACCADIVES, a group of coral reefs and islands in the Indian Ocean, lying between 10 and 12 20 N. Int. and 71 40 and 74 E. long. The name Laccadives (laksha divipa, the &quot;hundred thousand isles&quot;) is that given by the people of the continent, and was probably meant to include the myriad Maldives ; they are called by the natives simply Divi, &quot; islands,&quot; or Amendivi, from the chief island. There are about nineteen separate reefs, con taining, however, only thirteen islands, and of these only eight are inhabited. The islands have in nearly all cases emerged from the eastern and protected side of the reef, and have gradually extended towards the west over the shallow lagoon of which the rest of the space within the barrier-reef consists. The islands are small, none exceeding a mile in breadth, and lie so low that they would be hardly