LIG 



LIL 



nuclei, called shields, which break 

 through the upper surface of the Ihal- 

 lus, or main substance of the lichen, 

 are of a peculiar odour and texture, 

 and contain the reproductive parti- 

 cles. Lichens abound in the cold and 

 temperate parts of the world. Tlie 

 greater part are of no known use ; 

 but some, as the reindeer moss (Cc- 

 nomyce ranffifcrina), the Iceland moss 

 {Cctraria Islandica), and various spe- 

 cies of Gyrophora, are capable of sus- 

 taining life, cither in animals or man. 

 The Iceland moss, when deprived of 

 its bitterness by soaking in an alkali, 

 and then boiling, becomes, indeed, a 

 diet recommended to invalids. Oth- 

 ers are used as tonic medicines, as 

 Variolaria faginca and Parmclia pan- 

 ctina. Their principal use is, how- 

 ever, that of furnishing the dyer with 

 brUhant colours ; orchalL, cudbear, 

 and peroUe, with many more, are 

 thus employed."' 



LIFTING PUMP. See Pump. 



LIGAMENTS. Elastic fibrous tex- 

 tures uniting the bones together. 



LIGATURE. A bandage. In hor- 

 ticulture, bass is used chiefly for thhs 

 purpose. In farriery, a ligature is a 

 fine, strong thread of silk, with which 

 blood-vessels, &c., are tied in opera- 

 tions. 



LIGHT. An imponderable agent, 

 emitted in great brilliancy by the sun : 

 it travels in straight lines at the rate 

 of 192,000 miles the second. The 

 sun's light consists of seven different 

 colours, red, orange, yellow, green, 

 blue, indigo, violet, which, being uni- 

 ted, make the white light : they may 

 be separated by a prism of glass, or 

 a coloured transparent body. 



Light is a most important agent in 

 the development of plants, the green 

 colour of their herbage being produ- 

 ced by its action ; it appears to be 

 the yellow light that effects this re- 

 sult. Although mould, and some 

 kinds of mushrooms, exist without 

 light, the plants usually cultivated 

 cannot exist without its presence ; 

 hence, few plants do well in the shade. 

 The bending of stems towards the 

 light is one of the most curious phe- 

 nomena of vegetation ; it seems to 



be produced by the blue and indigo 

 rays. 



A pencil of light is a small beam, 

 the parts of which are divergent. 



LIGHTNING. The discharge of 

 electricity from immense surfaces of 

 clouds ; it may occur from one cloud 

 to another, or to the earth ; in the 

 latter case, the highest points and the 

 best conductors receive the stroke. 

 Hence, rods of iron one inch or more 

 thick, and rising four to ten feet above 

 buildings, are used for protection ; 

 the upper ends should be beaten out 

 into several points, and either gilded 

 or covered with platina, and the low- 

 est extremity buried in the earth sev- 

 eral feet, or brought in contact with 

 moisture ; in cities, the iron or lead 

 pipes circulating through the streets 

 form a good point of attachment. In 

 a large building several rods are want- 

 ed. Large trees are admirable con- 

 ductors of lightning, but, as their bark 

 is often torn off violently during the 

 passage of the fluid, it is dangerous 

 to take shelter near them. 



LIGNEOUS (from lignum, wood). 

 Wood-like. 



LIGNIN. The pure fibre of wood 

 divested of starch and other impuri- 

 ties ; according to Payen, it consists 

 of an investing or cellular matter, 

 cellulose, Ci; Hio Oio, isomeric with 

 starch, the true internal matter, or 

 lignin, being Or, H-4 0:o. Fine linen 

 from hemp or flax is insoluble in wa- 

 ter, decays very slowly, and is con- 

 verted into dextrine by the action of 

 ddute sulphuric acid and heat, and 

 finally into starch sugar. 



LIGNIPERDOUS INSECTS. 

 Those insects which bore into or oth- 

 erwise destroy wood. 



LIGNITE. A kind of partially- 

 formed coal, in which the woody 

 structure is distinct. It belongs to 

 the secondary formations. 



LIGULA. An appendage of the 

 sheathing petioles of some .grasses. 

 The lower lip, or labrum, of insects. 



LIGUL.\TE. Shaped like a rib- 

 and. The outer florets of some 

 composite flowers are called ligu- 

 late. 



LILAC. Syringa vulgaris. A beau 



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