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TOUCH.—SMELL.—TASTE.—CHEMICAL CONSTITUTION. 75 TOUCH. 269. This character is so limited in its application as to be of little service in distinguishing minerals. Steatites have a more or less greasy feel; and dry pulverulent substances, as chalk, ar e what is termed meagre to the touch. Between these ex tremes there are intermediate degrees and kinds of sensation experienced by the touch, but they are not of sufficient im portance to have received much attention from mineralogists. SMELL. 270. Some minerals emit an earthy smell when breathed upon ; others produce peculiar odours when struck with a ham mer : that so produced in some of the ores of cobalt and arsenic resembles garlic; those of selenium, when heated, exhale the odour of horseradish ; and sulphurets that of sulphur; and some varieties of calcite, which, in consequence, bear the name °f stinkstone, give out an offensive smell when broken. But it is a very unimportant character, except as to its being the means of detecting the presence of selenium, arsenic, and sul phur in minerals. TASTE. 271. This quality is perceivable in only the few soluble sub stances which are admitted as mineralogical species, and will be noticed in their several descriptions. CHEMICAL CONSTITUTION. 272. There are known at present sixty-two elementary or undecomposcd substances, which, with the exception ot some recently discovered, of which the properties are not yet fully ascertained, may be classed as follows:— 1. Non-metallic elements.—Imperfect conductors of elec tricity and heat. Gaseous.— Oxygen, hydrogen, nitrogen, chlorine, fluorine. Liquid.—Bromine. Solid.—Carbon, phosphorus, sulphur, boron, selenium, iodine, silicon. 2. Metallic elements.—Good conductors of electricity and heat, with the exception of mercury solid. <*■ Light metals, having a strong affinity for oxygen. Metals of alcalics and alcaline earths.—Potassium, sodium, lithium, baryum, strontium, calcium. Metals of earths.—Magnesium, lanthanium, yttrium, glucium, aluminium, zirconium. b. Heavy metals. a. Metals not reducible to a metallic state by heat alone. E 2