LAPIDARY 39 



more fluent than the latter. Sperm-oil, when heated to 265 Fahr., runs off in 300 

 seconds, or |th of the time it took when at the temperature of 64. Southern whale 

 oil, having a greater density than the sperm-oil, would flow off faster were it not 

 more viscid. 2,000 grain-measures of water at 60 run off through the said siphon in 

 75 seconds, but when heated to 180 they run off in 61 seconds. Concentrated sul- 

 phuric acid, though possessing the great density of 1'840, yet flows off very slowly at 

 64, on account of its viscidity, whence its name of oil of vitriol. 2,000 grain-measures 

 of it took 660 seconds to discharge. 



For a continuation of this subject, and a further description of lamps of various 

 kinds, see. also SILBER LIGHT ; SAFETY LAMP. 



LAIMPIC ACID. Syn. Aldehydic acid ; Acetylous acid. (Acide lampique, Fr.) 

 If a little ether be placed at the bottom of a glass, and some spongy platinum attached 

 to a wire of the same metal be ignited and suspended about an inch from the fluid, 

 it will glow and continue to do so for a long time. On the other hand, if a spiral of 

 platinum wire be placed over the wick of a spirit-lamp, and the latter be first ignited 

 and then blown out, the wire will continue at a red heat until all the spirit is ex- 

 hausted. Numerous sesquioxides, when placed warm on wire-gauze over capsules 

 containing alcohol, will glow in the same manner. Under all these circumstances, a 

 powerful odour resembling aldehyde is evolved, which strongly affects the eyes. If 

 this experiment be made in such a manner that the volatile product may be condensed, 

 it will be found to be strongly acid. It is powerfully reducing in its tendency, and 

 if heated with the oxides of silver or gold, converts them into the metallic state, and 

 the liquid is found to contain acetic acid and resin of aldehyde. If, however, the 

 acid liquid be only very gently warmed with oxide of silver, a portion of the latter is 

 dissolved ; but when baryta is added to precipitate the silver as oxide, and the fluid 

 is warmed, the metal instead of the oxide comes down, and the fluid, when tested for 

 the nature of the acid, is found to contain nothing but acetate of baryta. These 

 phenomena are explained by some chemists by supposing the fluid to contain an acid 

 which they, following the late Professor Daniell, call the lampic, and supposed to 

 contain C 4 H 4 S (C 4 H 8 O 3 ). When lampic acid is treated first with oxide of silver, and 

 then with baryta-water, and heated, they consider that the oxygen of the oxide of 

 silver is transferred to 'the lampic acid, and converting it into acetic acid, which com- 

 bines with the baryta, while the metallic silver is precipitated. The following equa- 

 tion explains the reaction supposed to take place: 



C 4 H 4 3 + BaO + AgO = C 4 H 3 O s ,BaO + Ag + HO. 



Lampic acid. Acetate of baryta. 



C 4 H 8 O 3 + BaO + Ag 2 O = (C 2 H 3 O 2 ) 2 Ba + Ag' - 



The conversion of the lampic acid into acetic acid is therefore attributed to the oxidis- 

 ing tendency of the oxide of silver. Those who regard the decomposition from the 

 above point of view, consider lampic acid to be acetylous acid, that is to say, to bear 

 the same relation to acetylic acid (acetic acid) that sulphurous acid does to sulphuric 

 acid. 



XiAAXBSKICTS. With the fleece on, these are extensively used for clothing, for 

 door-mats, and the like. Prussian lambskins are used for linings, for coat collars and 

 cuffs. Astracan lamb, which is a rich, glossy, black skin, with short fur, is used for 

 many ornamental costumes. Hungarian lamb : this skin forms the national coat of 

 Hungary. Spanish lamb : the short jacket of the Spaniard is made of this skin. 

 It is said that upwards of a million lambskins are imported annually into this country 

 for glove-making. 



XiAXrARXEITE. A sulphato-carbonate of lead occurring at Leadhills in Lanark- 

 shire, whence the name. 



EiAETCE WOOD. Uvaria lanccolata or Guatteria virgata. This wood is imported 

 from Jamaica and Cuba, in long poles from 3 to 6 inches diameter. Lance wood is 

 paler in colour than box ; it is selected for elastic works, as gig-shafts, archery bows, 

 springs, &c. These are bent into the required form by boiling or steaming. Sur- 

 veyor's rods, ordinary rules, and billiard cues are made of lance wood. 



Ii-awDESJ. In mining, the man who attends at the mouth of the shaft to receive 

 the ' kibble of ore' as it reaches the surface. 



IiAWGITE. A basic sulphate of copper, from Cornwall, described a few years 

 ago by Prof. Maskelyne. 



XiATCTHAlffUItX. Ametal discovered by Mowinder in 1841. It occurs associated 

 with oidymium and cerium, in certain rare Swedish minerals. 



XAPIBARY, Art of. The art of the lapidary, or that of cutting, polishing, and 

 engraving gems, was known to the ancients, many of whom have left admirable spe- 



