LEV- 



LEV 



most hardy are tlie larj^e green head, 

 cabbage, tennis ball, Ejiyptian green 

 coss, larged green curled, and .Ma<lei- 

 ra, which may be kept alive tlirough 

 winter if protected by a coating of 

 straw: they are sown in Sepleiiibcr. 

 Other esteemed spring kinds are the 

 early Silesia, sugar luaf, Paris loaf 

 coss, pale green, and a later sort, 

 the large summer Silesia. Lettuces 

 in this latitude require to be raised 

 in slightly warmed beds. An ounce 

 of seed produces upward of ten thou- 

 sand plants. It should be sown very 

 thin early in March, and transplanted 

 when about one inch and a half high, 

 as soon as the frost is out of the 

 ground. The soil should be rich and 

 fine, and the plants set a foot apart 

 each way. They must be well wa- 

 tered after transplanting, for the let- 

 tuce is partial to moisture. The 

 plant must be kept weeded and well 

 worked, at least every fortnight ; in 

 this way they will head before hot 

 weather, after which they usually run 

 to seed without heading. The coss 

 lettuces required to be blanched by 

 tying up the leaves with a bass band- 

 age. Seed plants are procured by 

 allowing fine specimens to flower : 

 the seed sown should be fresh, as it 

 frequently loses its vegetating power 

 after two years. 



LETTUCE, LAMB'S. Corn salad. 



LEVIGATION. The reduction of 

 hard substances, by rubbing or tntu- 

 ration, to fine powder. 



L E U C I N. A white, crystalline 

 body like spermaceti, produced by the 

 action of alkalies or sulphuric acid 

 on protein : formula, Cjo H1.2 N O4 



LEU CITE. White Vesuvian 

 garnet. It is abundant in some of 

 the Vesuvian lavas, and contains up- 

 ward of 23 per cent, potash, alumina 

 23, silica 54. 



LEUCOL. One of the products of 

 the distillation of coal tar. 



LEUCOMA. Opacity of the cor- 

 nea, which becomes whitish. 



LEUCOPHLEGMATIC. A con- 

 dition of the body in which the skin 

 is pale and flabby. 



LEVATOR MUSCLES. Those 

 which raise a limb or part. They are 

 '156 



situated in the front portions of the 

 animal. 



LEVEE. A provincial name for a 

 large embankment. 



LEVEL. An instrument for as- 

 certaining the level or the direction 

 of a horizontal line. It is of great 

 utility in drainage, building, and lay- 

 ing out grounds. 



Levels in which the plumb-line 

 forms the essential part are those 

 most usually employed for the com- 

 mon purposes required by bricklayers, 

 masons, carpenters, &c. They are 

 constructed under many ditTerent 

 forms, but the general principle is as 

 follows : A frame or board is prepared, 

 having one edge perfectly straight, 

 and an upright line is drawn on the 

 frame at right angles to the straight 

 edge. To some point of this line a 

 thread carrying a plummet is attach- 

 ed ; consequently, when the frame 

 is placed in such a position that the 

 thread of the plummet, hanging free- 

 ly, coincides with the upright line, the 

 straight edge of the frame, which is 

 at right angles, must be horizontal. 

 See Plummet. 



Spirit Level. — By far the most con- 

 venient and accurate level is the spir- 

 it level {F}g. 1), p,^ , 

 " which is noth- 

 ing more than a 

 glass tube near- 

 ly filled with spirit of wine, the bub- 

 ble in which, when the tube is placed 

 horizontally, would rest indifTerently 

 in any part, if the tube could be made 

 mathematically straight ; but that is 

 impossible to exe- 

 cute, every tube hav- 

 ing some slight cur- 

 vature." 



The spirit level 

 in surveyors' instru- 

 ments is fixed to a 

 frame carrying a tel- 

 escope or compass ; 

 Fionrc 2 represents a 

 spirit level mounted 

 on a staff, for com- 

 mon farm levelling. 



" It is furnished 



■ with eyesights, a h, 



and when in use is 



