SUPERIOR. 707 SUPERPHOSPHATE. Minn.; at the mouth of the Saint Louis and Nemadji rivers, on three bays, inlets of Lake Superior, and on the Northern Pacific, the East- ern Minnesota, the Saint Paul and Duluth, the Duluth, South Shore and Atlantic, the Great Northern, and the Chicago, Saint Paul, Minne- apolis and Omaha railroads (Jlap: Wisconsin, A 2). It is connected with Duluth by two rail- road bridges and by ferrj*. The city is finely situated. It is the seat of a State Normal School, and among other features are a public library, with more than 13,000 volumes, and Saint Mary's Hospital. An excellent harbor, which has been enlarged and improved through national. State, and city appropriations, and good transportation facilities have contributed to Superior's commercial importance. In the year ending June 30, 1901, the total foreign trade was valued at $7,353,553, including exports to the amount of .$G, 046,547. Wheat, corn, flour, lard and other meat products, iron and steel, cement, and lumber compose the ju'incipal shipments. The various industries in the census year 1900 had an invested capital of $5,882,562, and a pro- duction valued at $7,527,703. There are lumber mills, foundries and machine shops, breweries, flour mills, boiler shops, iron works, manufac- tories of chairs and windmills, and shipbuilding interests. The government is vested in a mayor, elected biennially, and a unicameral council; and in ad- ministrative officials, the majority of whom are appointed by the mayor, subject to the confirma- tion of the council. For maintenance and opera- tion, the city spends annually about $409,000, the chief items being: schools, $120,000: fire de- partment, $25,000; interest on debt, $23,000: and streets, $19,000. Population, in 1890, 11,983; in 1900, 31,091. On the site of Superior Radisson and Gros- seilliers are supposed to have made their head- quarters in 1061. Here in 1680 the famous ex- plorer Du L'Hut established a trading post. Su- perior was first laid out in 1855, and in 1885 the city was considerably enlarged, a company headed by Gen. J. H. Hammond having laid out an addition west of the original town. In 1881 the Northern Pacific Railroad Company built a branch liither. SUPERIOR, Lake. The largest and most northerly of the Great Lakes of North America, and the largest body of fresh water in the world (Map: America, North, K 5). It is situated a little to the northeast of the centre of the conti- nent, and is bounded on the north and east by the Canadian Province of Ontario, and on the south by the State of Michigan and a part of Minnesota, the latter State forming also the western boundary. Its shape is nearly a cres- cent, the horns extending southwest and south- east, while the large Keweenaw Peninsula reaches nearly to the centre of the lake from the middle of the southern coast. Lake Superior has a coast line of 1500 miles; its extreme length from east to west is 412 miles; its extreme breadth is 167 miles. Area, 31.200 square miles. Its mean elevation above sea level is 602 feet, and it lies 20 feet above the level of Lake Huron, into which it discharges through the Saint Mary's River (q.v.). It receives a large number of streams, but they are all short, the basin of the lake being closely hemmed in by the water- sheds of the Mississippi and of Hudson Bay. The principal stream entering it is the Saint Louis River, which falls into the extreme western end of the lake, and is considered as the farthest headstreani of the Saint Lawrence. The shores of Lake Superior, except in the southeast, where there are long lines of sand dunes, are generally bold and rocky. On the Jlichigan shore are the celebrated sandstone clili's known as Pictured Rocks, which are streaked by the red and yellow deposits of fer- ruginous waters. In many places, especially along the Canadian shore, there are precipitous clilVs of basalt rising directly from the water to a sheer height of from 300 to" over 1000 feet, such as Thunder Cape on the northwest shore. The north shore is also cut up into deep bays sur- rounded by high clifi's, and forming good har- bors, and it is lined with a number of high, rocky islands with precipitous sides and capped by eruptive material. In the greater part of the lake, however, the islands are few, the largest being Isle Royal, 45 miles long and 8 miles wide, belonging to Michigan. In general the country surrounding the lake is covered with pine forests. Lake Superior is deeper than any of the other Great Lakes, its maximum depth being 1008 feet, so that the bottom lies 400 feet below sea level. The water is very clear, and so fresh as to be al- most chemically pure. It is cold throughout the year to within a few feet of the surface, and in the deeper portions maintains a nearly uni- form temperature of 39°. The lake never freezes except in the shallow water along the shores. The level of the lake is subject to several sets of periodic changes, partly owing to changes in rainfall and evaporation and ])artly to the winds; a long continued storm will sometimes raise the leeward level seven feet above the nor- mal. Violent storms occasionally sweep over the lake, when tlie waves may attain an amplitude of 15 or 18 feet. The basin of Lake Superior is remarkable as being unrelated to those of the other Great Lakes. While the latter are river valleys scooped out of the softer strata of the ancient coastal plain lying northwest of the Appalachian Plateau and skirting the Archa>an continent, Lake Su- perior lies almost wholly within the Archtean region. The most recent investigators are of the opinion that this basin is a primitive depression in the earth's crust antedating the Huronian pe- riod. The numerous intrusions of eruptive rocks w'hich encircle the lake are arranged roughly in concentric circles, the most recent being found nearest the lake, and it has been suggested that the depression is an ancient and deep-seated cen- tre of volcanic activity. The formation of the lakes themselves, however, is due to the obstruc- tion of the valleys during the Glacial Period. The country surrounding the lake is rich in min- erals, and large veins of copper and iron ore traverse its bottom from the southern shore. Consult Agassiz, Lake Superior: Its Pln/fiical Character. Vefjetation, and Animals (Boston, 1850). For commerce and navigation on the lake, see Gre.t L.^kes. SUPERPHOSPHATE. An orthophosphate in which only a portion of the hydrogen of the orthophosphoric acid has been replaced by a basic radical. The most important superphosphate, agriculturally, that of lime, menocaleium phos- phate (Ca0.2H,O.P.O,). is prepared by treating tricalcium phosphate ( [CaOlj.PA.) in' the form
