« ПретходнаНастави »
75. All the substances which form the ground and earth, are called minerals. Clay is a mineral; all stones are minerals; coal is a mineral; chalk, and, in short, whatever is not animal or vegetable, is called mineral.
76. The study of minerals has been methodised, and called the science of mineralogy. In this, as in many other branches of science, little
more, has been effected, than to attain a systematic classifi. cation and nomenclature.
77. All minerals, i.e. all earths, soils, stones, and metals, are scientifically divided into four classes. 1. Earthy Minerals--being all such, as are void of
taste and smell, light and brittle ; as millstone, flint or silex, clay, sand, crystals, spar, gypsum, alabaster, chalk, stones, cornelions, jasper, topazes, sapphires,
rubies, emeralds, and diamonds. 11. Saline Minerals—being such, as have a pungent
taste, and are heavier, softer, and partly transparent; as common salt, alum, nitre or salt-petre, and
borax. III. Inflammable Minerals—being lighter, brittle, opa
que, and never feeling cold; as coals, sulphur,
black-lead, and amber. IV. Metallic Minerals--being heavier, opaque, cold,
ductile, capable of being drawn into wire, and malleable, capable of being worked into shape. These consist of gold, silver, &c. see paragraph in another part of the work for further particulars.
78. Many metals exposed to the air become dusty ; that is to say, they imbibe a part of the air called oxygen, and the rust is called an oxide. If melted and heated on a fire for a considerable time, they also imbībe
oxygen from the atmosphere; and turn into substances called oxides: the process is called oxidation.
79. If 10 lbs. of lead be melted and heated in this manner, it will be converted into an oxide called red lead; and the red lead so produced, will be found to
weigh 11 lbs. the additional pound arising from the imbibed oxygen.
80. Oxides may be converted into metals again, by depriving them of their oxygen. In the example of red lead, if it be burnt again with powdered charcoal, the charcoal will detach the oxygen from the oxide, and the lead will be obtained again in its pure state: this process is called reduction.
81. Modern chemists consider the whole earth as metallic; and all the different earths to be nothing more than various oxides, or rusts of metals, produced by the continued action of the air and water on them; and capable, by suitable means, of being reconverted into metals !
82. Platina is the heaviest of all metals, being 23 times heavier than water; but it is a modern discovery. The colour is light grey, and it cannot be melted in ordinary fires.
83. Gold is 19 times heavier than water; and the most valuable of all the metals. It is so malleable, that an ounce of it will gild a silver wire 13,000 miles in length: and it may be beaten into leaves; 300,000 of which, are only the thickness of an inch.
84. Silver is 11 times heavier than water; and next to gold in beauty ; such is its ductility, that it may be drawn out in wire finer than a hair.
85. Mercury, or Quicksilver, is 14 times heavier than water ; and is remarkable for being liquid like water; and for not becoming solid except in cold greater than that which renders water solid.
86. Copper is 9 times heavier than water; and is found in great abundance in the mines in Sweden, and also in the isle of Anglesey. It unites well with other metals; and forms a variety of useful compounds.
87. Iron is 8 times heavier than water; and is the most useful, and, in England, the most abundant of all the metals. It mixes with the animal, vegetable, and mineral kingdoms. It is melted with more difficulty
than gold, silver, or copper; and it usefully strikes fire with flint.
Obs.--The loadstone, which possesses the singular and un. accountable property of always pointing to the north, is an ore of iron.
Red and yellow ochres are impure oxides of iron : generally where redness is found in the soil, the presence of iron may be suspected.
88, Tin is an English or Cornish metal, 7 times heavier than water. It is very malleable; and is highly useful as a coating to iron and copper; requiring only, to have iron dipt into it, and copper to be rubbed with it, to become perfectly coated.
89. Lead is 11 times heavier than water; easily melted,, and highly useful for various purposes.
90. Nickel is a Chinese metal of a light grey ; 9 times heavier than water, and melted with difficulty:
91. Zinc is 7 times heavier than water, of a bluish white colour, and used in various compounds.
92. The other metallic substances are Antimony, Bismuth, Cobalt, Arsenic, Manganese, Palladium, Rhodium, Potassium, &c. to the number of thirty; although the ancients knew of only seven metals.
93. Iron is formed into steel, by being heated with charcoal. Brass is composed of zinc and copper. Bell-metal is a mixture of tin and copper. Pewter is a mixture of tin and lead. Bronze is a mixture of copper and tin.
94. Coals are minerals dug out of the ground in immense mines; particularly at Newcastle, Whitehaven, and Wednesbury; and they are the best fuel yet discovered by man. The British islands are celebrated for their coal-mines; many countries being obliged to depend on wood; which is often scarce and dear. Obs.-Coals
are, in all probability, the remains of submerged forests, brought to their present state by some unknown process of subterranean chemistry.
95. Half the civilized employments of man, consist in working the metals and minerals. In England, the
large towns of Birmingham and Sheffield are wholly engaged in the useful and ornamental manufactures of various metals.
Obs.--All that boys effect with lead and a tobbaco-pipe, men effect in regard to all the metals, by similar or slightlyvaried meane.
96. Civilization depends so much on the discovery of the useful metals, that little progress can be made from a savage state, without the useful trade of a blacksmith.
He makes all the implements of gardening and age riculture ; all domestic utensils; knives to cut with; and spears and swords to defend the soil and its produce, against invaders.
97. To avoid the inconvenience of exchanging or bartering, men, in early ages, fixed on metals; as on gold, silver, copper, or iron, for a medium of value: so that, if one man had too much corn and wanted wine, he was not obliged to give corn for the wine, but he might sell his corn for so much metal, and buy the wine with the metal, at his convenience.
Obs.--Hence, the origin of money; and as it was found inconvenient to weigh, metal in every transaction, (as Abra. ham did when he bought the burying-place of Sarah); stamps were put on pieces of metal, as kings' heads, to indicate that they inig'st be safely received for a settled weight or valve. Hence, iu England, there are pieces of stamped gold of known value ; as guineas, half guineas, sovereigns, half sovereigns, &c. pieces of stamped silver, as crowns, shillings, &c. and pieces of stansped copper ; as pennies and half perpies : all of universal worth. The coins of the United States are eagles, valued at ten dollars, half eagles and quarter eagles, all in gold ; dollars, balf dollars, quarter dollars, dimes and half dimes, in silver ; and cents and half cents in copper. There is, also, an extensive paper currency, from the banking institutions which prevail throughout the country.
V. Of Building. 98. Man, like other animals, would seek places in which he might shelter himself from the inclemency of țlie weather. Beasts of prey retire to thickets and
saves; beavers build mud-houses, and rabbits make burrows under ground. Man, in his most savage state, imitates their practices; and then improves on them, by the aid of his reason.
99. Among savage tribes we find, at this day, that the Siberians and North Americans reside under ground; having their filthy habitations entirely closed during the winter months. In warmer regions, the Americans build wigwams of stakes and leaves, and turf, in the shape of a soldier's tent.
In Africa, the materials of the kraals or houses are the same as the wigwams; but the shape is circular, with a hole at the top to let out the smoke; and in order to keep out beasts of prey the enterance is so low, that the inhabitants crawl in and out.
100. A number of these subterranean habitations in one place; or a collection of wigwams or kraals, forms a Siberian, American, or African tribe. In many islands of the South Seas, the natives, when first discovered, had learnt to elevate the roofs on poles, and to fill in the sides of their houses with boughs or rushes, mud or sods.
Obs. The cottages of many of the poor, are still built in this manner in England; and few need travel a mile from their owu residence to see the original style of architecture.
101. Those nations which first raised the roofs of their houses on poles, were discoverers in this art. Those which first used stone, however rude, and mud or clay to fill up the interstices between the stones, and eement them together, made considerable improve ments.
After the discovery of iron and metals, when the axe, the hammer, the saw, and the plane, became the tools of builders, it may be supposed, that houses would soon be raised to two stories, and increased in size and convenience.
102. To make artificial and equally-shaped stones, by burning clay into bricks, was a further invention of