144 VOCABULARY OF 



Leyden Jar, a glass jar, coated with tin foil, for electrical purposes. 

 It received its name from the first contriver being a native of Ley- 

 den. See page 6 1 . 



Light, that power by which objects are made perceptible to our sense 

 of seeing. See page 25. 



Lightning, an electrical phenomenon preceding thunder. 



Liquid, the state of any body, in which by means of heat, the particles 

 slide over one another, and wet any substance that comes in contact 

 with it. Water, Oil, &c., are both liquids and fluids. Quicksilver is 

 fluid, but not a liquid. 



Lithium, a recently discovered metal, brought from Sweden. It is of 

 no practical use. 



Machine, any body intended to produce motion, so as to save either 

 time or strength. 



Magnesium, the metallic base of magnesia. 



Magnetism, the quality of a body rendered capable of attracting. See 

 page 13. 



Malleability, that property by which metals may be extended through 

 hammering. 



Manganese, a metal noted for its peculiar affinity for oxygen : it is very 

 generally diffused through all kinds of rocks, and is procured in great 

 abundance from different parts of England. In its pure metallic 

 form it is of a bright white colour; but through its affinity for oxygen, 

 if exposed to the air it will soon lose its metallic appearance, and 

 fall to powder. The metallic form is obtained by art, as its natural 

 state is an oxide. Manganese is used in glazing, and also in pre- 

 paring bleaching liquor. 



Matrix, the substance in which ores are imbedded in the earth. 



Mechanical Powers, engines used for raising weights. See page 67. 



Meniscus, a glass, convex on one side, and concave on the other. 



Menstruum, any fluid that will disssolve hard bodies. 



Mercury, another name for quicksilver, so called from its volatility. 

 Although its natural state is that of a fluid, it will become frozen at 

 about 40 below Zero, and is then both malleable and ductile. Mer- 

 cury will combine with several of the metals, which combinations 

 are called amalgams ; it also combines with sulphur, phosphorus, 

 &c. It has' very little affinity for oxygen, except when heated. 



Metals, are bodies known by their weight, ductility, &c. There are 

 said to be nearly forty kinds of Metals ; Platinum is the heaviest, 

 and Potassium the lightest. 



Metallic Oxides, metals combined with oxygen, when, from being com- 

 bustible, they become incombustible. 



Metallurgy, the art of extracting metals from the ore. 



Meteorology, the doctrine of the various phenomena of the atmosphere. 

 See page 53. 



Microscope, an optical instrument, formed by the combination of 

 lenses, to magnify small objects. 



Mineral, any substance, either of a metallic, earthy, or saline nature. 



Mineralogy, the science which treats of the properties of minerals. 

 Minium, a red oxide of lead. 



