USEFUL MINERALS. 



specific name to include several combustible sub- 

 -stances, the most important of which are naphtha, 

 petroleum, and asphalt or mineral pitch, all closely 

 resembling each other in chemical composition. 

 They are found both as liquids and solids. The 

 latter are dissolved by the former, and are also 

 soluble in alcohol They consist essentially of 

 carbon and hydrogen, but a little oxygen is also 

 present in the harder kinds of asphalt. From a 

 light limpid naphtha at one extreme, to a hard 

 rocky asphalt at the other, these bitumens possess 

 all degrees of consistency. 



The terms naphtha, petroleum, and rock-oil, as 

 now used, are vague and perplexing. When 

 applied to native products, they all really mean 

 the same thing. If there is any difference, 

 naphtha is only a lighter kind of petroleum, but 

 sometimes the one name, sometimes the other, is 

 applied to the very same substance. With arti- 

 ficial products such as the oils or liquid hydro- 

 carbons distilled from coal, those with the lowest 

 specific gravity are called naphthas, to distinguish 

 them from the heavier bodies of the same kind, 

 such as paraffine or burning oil, dead oil, &c. So, 

 also, when crude native petroleum is purified, the 

 lighter hydrocarbons obtained in the distillation 

 are called naphthas, and the heavier ones petro- 

 leum, kerosene, &c. There is this important dis- 

 tinction in these cases, that the lighter hydro- 

 carbons or 'naphthas' are more dangerous than 

 the heavier. The former can be burned with 

 safety in lamps of a peculiar construction, but not 

 so in ordinary petroleum or paraffine-oil lamps. 

 The vapour of these light bodies takes fire at, or 

 even under, 100 F., and they cannot be safely 

 used in ordinary lamps if their firing-point is 

 below 120 F. 



The petroleums or naphthas which have been 

 longest employed for lamp-oils and other useful 

 purposes are those found in Persia, in the Bur- 

 mese empire, on the shores of the Caspian Sea, 

 and in different parts of Italy. Most of these are 

 -easily purified, and have then a pleasant odour, a 

 .rare property among mineral oils. Considerable 

 quantities have been imported into England from 

 Baku and Rangoon, and, but for their high price, 

 these would soon supersede all other rock-oils in 

 the market. The great Pitch Lake of Trinidad, 

 about three miles in circumference from which 

 the lamp-oil called ' kerosene ' was first obtained 

 the petroleum springs and bitumen mines of 

 Cuba, and the oil-springs of the United States, 

 have also been long known as yielding valuable 

 bituminous products. But these substances, from 

 several causes, have attracted so much attention 

 of late years, that new supplies of them have been 

 discovered in various parts of South America, in 

 Canada, Siberia, and other countries. 



Of all the known sources of petroleum, by far 

 the most important is the coal region of the 

 United States. Several of the localities where it 

 is found were known to the Indians, by whom it 

 was at one time collected for sale ; but it is little 

 more than twenty years since the oil-wells were 

 sunk deep enough to give any considerable yield. 

 In a very few years the trade grew with astonish- 

 ing rapidity, for the shipments, which, in 1861, 

 were only 1,500,000 gallons, amounted in 1871 to 

 1 5 5)6 1 3,000 gallons. It is estimated that the 

 world's consumption of illuminating oil amounts 

 .to 1,800,000 gallons every day. The import of 



petroleum into the United Kingdom in 1884 was 

 5 2 >975>789 gallons, of the value of 1,711,313, of 



which 50,200,956 gallons came from America. 

 The total shipments of refined oil from America 

 in 1885 amounted to 6,985,637 barrels, of which 

 the United Kingdom received 1,269,723, London 

 taking 666,964 barrels. The production of mineral 

 oil from shale in Scotland, in 1885, was about 

 55,000,000 gallons of crude oil 



Besides being burned in lamps, naphtha is used 

 as a solvent for india-rubber, as a cheap sub- 

 stitute for turpentine, in the manufacture of lamp- 

 black for printers' ink, and some kinds of it for the 

 production of benzole, now so largely required in 

 the manufacture of aniline colours. 



Asphalt, or mineral pitch, is the name given 

 to a compact form of bitumen, which is usually 

 black or dark-brown in colour. When free from 

 earthy impurities, it has a conchoidal fracture and 

 resinous lustre. Asphalt is generally found wher- 

 ever rock-oil occurs, and in such localities it is 

 clearly produced by the drying up of the petro- 

 leum. In many places, however, it occurs in veins 

 or beds forming a compact rock. The Dead Sea, 

 some of the West Indian Islands, and one or two 

 places near the borders of France and Switzer- 

 land, are the best known localities for this sub- 

 stance ; but it is found, less or more, in a great 

 many countries. Asphalt was employed by the 

 ancient Egyptians for embalming their dead, and 

 it is said to have been used in Babylon as an 

 ingredient in mortar. Its modern applications 

 are numerous. It is an ingredient in Japan var- 

 nish, and is used along with other materials to 

 make water-proof roofing and flooring, linings for 

 cisterns, and in the construction of water-pipes. 

 It is much used now to form what are called 

 'damp courses' in walls that is, a layer of it 

 about two inches thick is spread over the thick- 

 ness of a wall near the ground-level, to prevent the 

 ascent of damp. One or two kinds, such as those 

 found at Seyssel in the east of France, and at Val- 

 de-Travers in Switzerland which, however, are 

 rather bituminous limestones than true asphalts 

 have, since 1854, been very extensively employed 

 in the construction of foot and carriage pavements 

 in Paris, and also, within the last two years, in 

 some of the busy parts of London. When this 

 material is used, there is, of course, far less noise 

 produced by the traffic on the streets than with 

 stone. Pavements formed of an artificial or coal- 

 tar asphalt have long been, to a limited extent, in 

 use ; but they have never been liked, on account 

 of their liability to soften with the heat of summer. 



jet. Some cannel coals which do not change 

 when exposed to the atmosphere, and which take 

 on a fair polish, are made, in the localities where 

 they are found, into bracelets, inkstands, vases, and 

 even tables. Others, again, although they have 

 much the same appearance at first, are totally 

 unfit for such purposes, as they are soon decom- 

 posed by the action of the atmosphere. In Phila- 

 delphia, boxes and small ornaments are made of 

 anthracite. 



The beautiful black substance jet, which, like 

 coal, is merely fossilised wood, is found in small 

 quantities in the Lias beds of Yorkshire, the pieces 

 varying from an ounce to two hundredweight 

 in weight. It likewise occurs along with amber 

 in the lignite beds of Germany, in Aude and other 

 departments of France, as well as in several other 



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