r '.i 



while in -ii. /in.-, lead, silver, and 



graphitp aro found m I'.ntish and 



other <>rd<>\ n-i.iii rooks. 



foaail remains are found of tins 



; notably graptolitc*, fora- 



mimfera, corals, star-fishe*. triln 



bites, brachiopods, gastropods, etc. 



Except for fishes, however, the 



^ of vertebrates are absent 



v ; Rooks. 



Ore. l?ronze coin of Denmark, 

 Sweden, and Norway; the one- 

 hundredth part of a krone (9.1'.). 

 It is coined in 

 I in iir/i- as MI 

 two-, and five-ore 

 pieces; ami in 

 silver as 1" 

 and 50-dre pieces. 

 Ore. Mineral 

 or rock mass con- 

 taining one or 

 more metals. The 

 term is only 

 applied to such 

 masses if the 

 Ore, Scandinavian metals are present 

 bronze coin, in quantity and 

 actual size form calculated 

 to make their extraction a pro- 

 fitable operation. Thus, granite 

 rock contains much potassium, and 

 common clay much aluminium, 

 but neither is regarded as an ore 

 on that account, because, with our 

 present knowledge, it would not 

 pay to extract the metal. 



The value of an ore depends on 

 the proportion of the metal or 

 metals present and the exact forms 

 in which they occur, which latter 

 circumstance will determine the 

 ease or difficulty with which the 

 metals can be extracted that is to 

 say, the cost of recovery. The pay- 

 able proportion varies immensely ; 

 thus ores containing less than 1 oz. 

 of gold to the ton are being worked 

 profitably to-day, but a mineral 

 carrying less than 30 p.c. of iron 

 would rarely be worked for that 

 metal. Iron, lead, or zinc ores con- 

 taining 50 p.c. of metal, and copper 

 ores carrying 25 p.c. metal are 

 rich ; while normal tin ore (tin 

 oxide) may have over 75 p.c. metal. 

 See Metallurgy ; Metal ; and names 

 of metals. 



Orebro. Town of Sweden, 

 capital of the Ian or co. of the same 

 name. It is a port of inland naviga- 

 tion at the W. end of Lake Hjalmar, 

 104 m. W. of Stockholm, and ex- 

 ports minerals from the local iron, 

 silver, and copper mines and the 

 tobacco, matches, paper, boots and 

 shoes, and machinery manufac- 

 tured in the town. An important 

 rly. junction with a connexion to 

 Christiania, it has the chief state 

 rly. workshops. The ancient castle, 

 now used as a museum, is in the 

 section of the town built on an 

 island in the Svarta Elf river ; the 



5809 



town hall ami an ..I, I church are 

 other buildings of noU. There is a 

 state technical college. The town 

 was long the place of assembly of 

 ,..!., I, .li.-t. wl.i.-h. in 1529, 

 made l.uili- mi m the state re- 

 ligion. l'..p. :u,000. 



Ore Deposits. In mineralogy, 

 iiiiiir.il !< miml.iii'.in of metalli- 

 ferous minerals in the earth's crust. 

 Tin- metallic ores are only occasion- 

 ally found pure, I i illy in 

 the form of o\i-l.--. sulphides, sul- 

 phates, carbonates, silicate - 

 the most noted exceptions being 

 gold and platinum found in tln-ir 

 natural state. Mixed with tin- 

 valuable metal ores are minerals, 

 usually not worth mining, and 

 kno\ui as gangue. Such gangue 

 constituents are quartz, felspar, 

 hornblende, calcite, etc. 



Ore deposits occur with most 

 metals except iron, in the form of 

 veins and lodes. These veins are 

 caused by the filling up of fissures 

 in the rocks by metallic deposits, 

 and from the nature of the action 

 the veins themselves may be a 

 mixture of several metals or metals 

 and gangue. The veins may be 

 practically any shape or run in any 

 direction, and be definite and clear 

 cut or ill-defined, according to the 

 nature of the parent rock. Such 

 vein deposits may vary in thickness 

 from an inch to hundreds of feet. 



Ores may occur more or less 

 evenly distributed throughout 

 certain rocks, particularly igneous 

 rocks, or appear as insoluble segre- 

 gation separated out from the 

 molten rock. Alluvial or placer 

 deposits are another form of ore 

 which have in the past produced 

 valuable finds, particularly of gold 

 and tin. Such deposits are caused 

 by the action of running water, See 

 Gold ; Iron ; Mining ; Silver, etc. 



Oregon. Name by which the 

 river Columbia (q.v.), N. America, 

 was first known. 



Oregon. Western maritime 

 state of the U.S.A. The surface is 

 extremely diversified. In the 

 mountainous W., the Coast Range 

 separates the rocky coast from the 

 fertile valleys of the Willamette and 

 Umpqua rivers, which are enclosed 

 on the E. by the Cascade Range, 

 containing many extinct volcanoes 

 and snow-capped peaks, the highest 

 of which is Mt. Hood, 11,225 ft 

 Further E. lies an undulating 

 prairie, scored by valleys and re- 

 lieved by numerous mountains, 

 and in the N.E. rise the Blue 

 Mountains. The Columbia river 

 marks most of the N. frontier, and 

 the Snake river a large part of the 

 E frontier, their valleys providing 

 an extensive tract of fertile land. 



The climate of W. Oregon is gen- * 

 erally mild and healthy, but farther 



O'REILLY 



K. there is a scarcity of rain, and an 

 extremely wide range of tempera- 

 ture. Over a large area in the 8. 

 there is no river drainage owing to 

 evaporation. Irrigati 

 are in progress. Wheat, hay, 

 potatoes, hops, and various fruit* 

 are produced, and the fisheries and 

 stock-raising are valuable Indus- 

 trie*. Gold, coal, silver, and other 

 ds are worked, while the 

 manufactures are chiefly associated 

 with land products and the fish- 

 eries. Oregon ranks fifth among 

 the states in the production . .f 

 lumber. There is a state university 

 at KuL'ene. and an agricultural col- 

 lege at Corvallis. The length of 

 the railways exceeds 3,000 m. 



Sal. 'in isth i ipital, and Portland 

 is the commercial centre. Two 

 senators and two representatives 

 are sent to Congress. Woman suf- 

 frage was adopted in 1912. Wash- 

 ington and Idaho, as well as parts 

 of Montana and Wyoming, were 

 originally included in Oregon, the 

 possession of which was long dis- 

 puted between Great Britain and 

 the U.S.A. It was jointly occupied 

 1818-46, when the frontier was 

 fixed at 49. The state was formed 

 out of the territory in 1859. Area, 

 90,699 sq. m. Pop. 783,000. See 

 History of Oregon, H. S. Lyman, 

 1903 ; History of the Pacific North- 

 West, J. Shaefer, 1917. 



Oreide OR OROIDE (Fr. or, gold ; 

 Gr. eidos, form). Brass introduced 

 in France as a substitute for gold 

 in the manufacture of jewelry. Its 

 composition is usually copper 85*5, 

 zinc 14'5 parts, and its colour 

 closely resembles that of real gold. 

 It takes a fine polish, is ductile and 

 tenacious, and can be readily 

 stamped, rolled, or worked. When 

 tarnished, its lustre may be re- 

 newed by washing with weak acid 

 solution. 



O'Reilly, JOHN BOYLK (1844- 

 90). Irish-American poet and 

 journalist. Born at Dowth Castle, 

 co. Meath, June 

 28. 1844, he 

 joined the 

 Fenian so 

 and in 1863 

 enlisted in the 

 British army in 

 order to induce 

 the soldiers to 

 revolt Tried 

 for high trea- 

 son in 1866, 

 and sentenced to be shot, the 

 sentence was commuted to 20 

 years' penal servitude in Aus- 

 tralia. Having managed to escape 

 to America in 1869, he settled at 

 Boston, where he became editor of 

 The Pilot, and published several 

 works in verse and prose. He died 

 at Hull, Mass., Aug. 10, 1890. 



J. B. O'Reilly, 

 Irish-American poet 



