LUBRICATING OIL 



143 



in the remotest degree any resemblance. During some primary convulsions, the 

 crust of the earth has been cracked, these fissures having, of course, some special re- 

 lation to the direction of the force which produced them. These cracks hare during 

 ages of submergence been filled in, according to some law of polarity, with mineral 

 matter, the character of the lode having generally some special relation to its direc- 

 tion. See MINING. 



LOGWOOD (Bois do Campcche, Bois bleu, Fr. ; Rlauliolz, Ger.) is the wood of 

 the Hcematoxylon Campechianum, a native tree of Central America, grown in Jamaica 

 since 1715. It was first introduced into England in the reign of Elizabeth, but as it 

 afforded to the unskilful dyers of her time a fugitive colour, it was not only prohibited 

 from being used, under severe penalties, but was ordered to bo burned wherever found, 

 by a law passed in the 23rd year of her reign. The same prejudice existed, and the 

 same law was enacted against indigo. At length, after a century of absurd prohibition, 

 these two most valuable tinctorial matters, by which all our hats, and the greater part 

 of our woollen cloths, are dyed, were allowed to be used. The logwood tree grows 

 from 40 to 50 feet high, the stems are cut into logs of about 3 feet long, the bark and 

 white sap (alburnum) of which are chipped off, the heart or red part only being sent 

 to England. Chevreul gave the constituents of logwood as volatile oil, tuematin, resin- 

 ous 'matter, tannin, glutinous matter, acetic acid, sundry salts of lime, with alumina, 

 silica, manganese, and iron. The decoction of logwood is of a deep dull red, which is 

 rendered paler and of a brighter colour by acids. Alkalis give it a purplish or violet 

 colour. Acetate of lead causes a blue, alum a violet precipitate ; the salts of iron 

 make it a dark violet blue, gelatine forming a reddish precipitate with it. The 

 colouring principle of logwood is a crystallisable substance known as hcematoxylin, 

 which contains C 16 iF0 6 (C IC H 14 O 6 ). 



Old wood, with black bark and with little of the white .alburnum, is preferred. 

 Logwood is denser than water, specific gravity, T057, very hard, of a fine compact 

 grain, and almost indestructible by the atmospheric elements ; it has a sweet and 

 astringent taste, and a peculiar but inoffensive smell, and will take a fine polish. 



When chipped logwood is for some time exposed to the air, it loses a portion of its 

 dyeing power. Its decoction absorbs the oxygen of the atmosphere, and then acquires 

 the property of precipitating with gelatine, which it had not before. The dry extract 

 of logwood, made from an old decoction, affords only a fugitive colour. 



For its applications in dyeing, see BLACK DYE ; CALICO PRINTING ; DYEING ; HAT 

 DYEING, &c. 



Imports of Logwood. 



An arsenide of iron, resembling mispickel. It is occasionally 

 auriferou?, and has been worked for gold at Keichenstein in Silesia. See PYKITES. 



X.OOKIKTC GZ.ASS. See MIRRORS. 



XiOOXVZ (Metier a tisscr, Fr. ; Webcrstuhl, Ger.) is the ancient and well-known 

 machine for weaving cloth by the decussation of a series of parallel threads, which 

 run lengthwise, called the warp or chain, with other threads thrown transversely with, 

 the shuttle, called the woof or weft. See JACQTJARD LOOM and WEAVING. 



XiOVACrE. The Levwticum officinalc, an umbelliferous plant, with aromatic 

 fruit. 



LUBRICANTS. Oleaginous or fatty bodies employed for the purpose of reducing 

 the friction between two parts of a machine or carriage. 



XiTra&XCATXNG OII. This name has recently been specially given to an oil 

 or grease prepared from the mineral naphthas. It ought to have a specific gravity 

 varying from 0-920 to 0'950, and to possess but a very slight odour. Although it 



