ALTO-RILIEVO 



217 



ALUMINUM 



workshops. It was incorporated as a borough 

 in 1854, as a city in 1868, and since 1914 the 

 government has been administered on the 

 commission plan. 



ALTO-RILIEVO, ahl' to rclya' vo (high re- 

 lief), is the term applied to sculpture when 

 the figures stand out more than one-half their 

 thickness from the background without being 

 entirely detached. On the so-called metopes, 

 labs of marble which topped the columns 

 of the Pantheon (which see), there are some 

 wonderful examples of figures in high relief. 

 The sculptures at the sides of the base of the 

 Nelson Monument in Trafalgar Square, Lon- 

 don, are also sculptured in this manner. See 

 BAS-RELIEF; MEZZO-RILIEVO. 



ALTRUISM, a/' truizm, a word which 

 means literally otherism, or thoughtfulness for 

 others above self, and stands for the belief 

 that the individual should subordinate his 

 personal feelings and sacrifice himself to the 

 welfare of society. The word was coined by 

 the French philosopher Comte from the Latin 

 word alter, meaning other, and the theory was 

 worked out by him. It is the opposite of 

 egoism, which makes self-benefit always the 

 motive for conduct. Pure altruism is impos- 

 sible, because everyone who has tested the 

 theory in any degree has learned that the indi- 

 vidual secures his own happiness in the hap- 

 piness of others. The truly charitable person, 

 who sacrifices himself that he may make others 

 happy, attains in the end greater happiness 

 than the selfish man, and thus to that extent 

 may be reckoned an egoist. While there still 

 remains an occasional philosopher who holds 

 that self-assertion or self-development should 

 be the main principle of life, society as a 

 whole realizes that there can be no real prog- 

 ress unless each person has due regard for the 

 interests of his fellowmen. 



ALUM, al' um, a substance used to adulter- 

 ate cheap baking powders, to harden fats and 

 tallow, to fix colors in dyeing and also in the 

 tanning of leather. Alum is a powerful astrin- 

 gent (which see) and if taken internally in 

 large quantities seriously injures the digestive 

 system. An ounce of alum, taken by mistake 

 for Epsom salts, has been known to burn the 

 throat, stomach and other organs so that death 

 resulted in a short time. It is a disputed 

 question, whether the quantity of alum used 

 in making baking powders is harmful ; in some 

 of the states of the American Union its use 

 for this purpose is forbidden. It is used in 

 medicine as an emetic, notably in cases of 



lead poisoning, as a means of stopping hem- 

 orrhages, and for various other purposes. 



Common alum, sometimes called potash 

 alum, is the result of the decomposition of a 

 variety of sandstone called alum stone or alum 

 shale. If the shale is broken up by exposure 

 to the weather, iron pyrite in the rock dis- 

 solves, and the sulphur combines with the 

 alumina to form aluminum sulphate, which 

 is made into alum by adding potassium sul- 

 phate. The shale may also be decomposed 

 by roasting. Common alum is a clear, colorless 

 solid, usually in the form of crystals; when 

 heated it turns to a fine powder, called burnt 

 alum. It dissolves readily in water, and has 

 a peculiar puckery taste. 



Most of the alum of commerce to-day is 

 not potash alum but ammonium alum, ammo- 

 nium being substituted for potassium. The 

 latter is much cheaper and for most purposes 

 is as useful, though it does not dissolve as 

 readily in water. The ammonium sulphate is 

 a by-product in the manufacture of illumi- 

 nating gas. 



ALUMINA, a In' mina, the oxide of alumi- 

 num, in its purest forms known as bauxite and 

 corundum; its varieties include the amethyst, 

 ruby, sapphire, topaz and emery, and in other 

 forms it is known almost everywhere. It 

 enters in large quantity into the composition 

 of granite, traps, slates, schists, clays, loams 

 and other rocks. The porcelain clays and 

 kaolins contain about half their weight of this 

 earth, to which they owe their most valuable 

 properties. It has a strong affinity for color- 

 ing matters, which causes it to be employed 

 in the preparation of the colors called lakes, 

 used in dyeing and calico printing. See 

 < )\IDK; ALUMINUM. 



ALUMINUM, alu'minum, or ALUMIN- 

 IUM, alyumin' turn, the most abundant and 

 one of the lightest of all metals, and with 

 the exception of silicon and oxygen the most 

 \\il.-ly distributed element in the earth's crust. 

 It is a whitish substance, with a slightly bluish 

 tint, a little harder than tin, which it resem- 

 bles. It is about two and one-half times as 

 heavy as water, but it is only one-third as 

 heavy as iron, a little more than one-fourth 

 as heavy as copper, almost exactly one-fourth 

 as heavy as silver and one-seventh as heavy 

 as gold. In tensile strength it excels all the 

 other metals except iron and copper; yet it 

 may be hammered into sheets or drawn into 

 wires like gold or sjlver. It requires a heat 

 of 1160 F. to melt it. 



