Stories of Minnesota climate are based on the extraordinary experiences of ex plorers and settlers rather than on the weather records; but even these experiences show a wide divergence. For instance Le Seuer's sec retary reports that in 1700 the rivers were frozen in September, and Carver declares that the winter of 1766 was so warm that he could live in the open without discomfort. Plowing has been accomplished in February and snow has blocked trains in October. It is of record that the mean annual temperature of the south eastern part of the State is 46° F., at the Twin Cities 44° and 36° in northern Minnesota. The coldest month is January, during which the mean temperature is 14° in the southeast, 12° at Saint Paul and 0° in the north. July is the warmest month, the temperature varying from 76° in the southern part, 74° at Saint Paul and Minneapolis to 68° in the north. It is seldom that extreme temperatures prevail for more than a day or two at a time and the State has been remarkably free from destructive storms. In fact since its settlement in the fifties only four dangerous tornadoes and three blockading snows have occurred. The rainfall is 22 inches in the lower Red River Valley, 28 at the Twin Cities, Rainy Lake or Lake Superior, and 34 in southeastern Minnesota. The elevation of the State, its fine drainage system and the dry ness of its atmosphere, especially in the winter, contribute to make it one of the most health ful regions in the world. At the Twin Cities the death rate is only 10 per thousand annually.
Soil.— The prevailing soil is a black loam underlaid by clay. This soil is deep and rich in the southern part of the State and in the Red River Valley. It is somewhat more shal low and sandier in the belt that skirts the pine woods, and quite sandy in the northeastern part. In the northern part are swampy tracts which, as they are being drained, add largely to the fertile acreage. The heavy soil produces all the varieties of grains and grasses, the sandy soil, clovers and potatoes, vegetables and fruit. With the exception of some rocky land in the northern part, a great deal of which is being reserved for a permanent white pine forest, there is scarcely any land in the State that is not productive or that does not promise to be productive as soon as it can be reached with the necessary improvements, either ditching or clearing.
Geology.— The surface of Minnesota, ex cepting the southeastern corner, is of glacial drift. Under this drift are found rocks of all ages. On the international boundary extend in g east to Lake Superior from Lake of the Woods and thence southwestward to 'the Min nesota River between Big Stone and New Ulm but terminating southwest of the river occur the gneisses, schists and granites of the Archa ian, or earliest, geologic age. Granite Falls in the upper Minnesota is formed by a granite out crop. Of the second geologic period, the Pale czoic, the earliest, or Cambrian, limestones and sandstones occur from Taylor's Falls on the Saint Croix and Kettle rivers southwest to the Minnesota and Blue Earth rivers, and along the Saint Croix and Mississippi to the south eastern part of the State. Lower Cambrian, or
red sandstone conglomerate and trappean rocks, are found on the border of Lake Superior and in Pine, Chicago and Kanebec counties in the eastern part of the State. In southwestern Minnesota this formation is found as red quartzite, or the pipestone and jasper of which the Indians were very fond. Rocks of the sec ond system of the Paleozoic Age, Silurian lime stones and shales are found from Minneapolis south to northeastern Iowa, and those of the Devonian, or third system, extend through Fill more and Mower counties into Iowa. Of the Mezozoic, or third geologic age, including Car boniferous, or coal-bearing limestones, Minne sota has none; but of the Cenozoic, or fourth great system, rocks are found over the western two-thirds of the State. These belong to the Cretaceous, or earliest period of this age and are the basis of the Coteau des Prairies in the southwestern part.
The glacial sheet, which covered almost the entire State, receding, left its drift to an aver age depth of 100 feet. Twelve marginal mo raines marking the successive outlines of the front of the ice sheet have been mapped. These cross Minnesota. Their ridges and knolls contain large boulders. In the Red River Valley, sloping southward in the direc tion of the ice recession, a great ice-dammed lake — called Lake Agassiz by the geologists was formed and held by the waning ice sheet. This lake attained a length of 700 miles and extended into Montana with a width of over 200 miles. It thus had an area of about 110, 000 square miles. Many ridges of sand and gravel reveal the beach lines of the lake, which. as it was lowered, ceased to drain southward through the Minnesota and Mississippi rivers and was finally reduced in size to Lake Winne peg, leaving behind the present Red River Val ley, the most fertile wheat land in the world.
Minerals.— Minnesota produces more iron ore than any other district in the world. In 1884 the first mines were opened in the Ver million Range and for the first 20 years pro duced 1,000,000 tons annually. In 1892 the Me sabe Range was opened and in 10 years aver aged 5,000,000 tons a year. During the next 15 years these ranges averaged nearly 25,000,000 tons a year. In 1910 the Cuyuna Range, ex tending southwestward from the Mesabe for 50 miles, was opened. It has yielded an annual output of approximately 1,000,000 tons. From the beginning of mining in the State a grand total of 500,000,000 tons have been shipped. In 1917 the production was 45,398,787 tons. The school of mines of the University of Minne sota estimates that there are 1,500,000,000 tons of merchantable ore remaining on the different ranges. This estimate does notprovide for possible discoveries still to be made by which a great deal of ore may become merchantable. A great deal of the mining is of the open-pit character. Steam shovels load the ore on trains that are run directly to the docks at Two Harbors or Duluth where steamers wait to carry it to the steel centres at Chicago, Gary or Erie. See article on DULUTH.