The Physiographic Expression of the Indian Creek Plutons of the Denver Mountain Parks Region, Colorado

to predict what may be expected in the future. Assuming that geographic conditions in any area are relatively constant, a farmer or investor, by scanning these maps, can make an intelligent estimate as tö what he may expect different percentages of the time with respect to the yield of corn or wheat per acre. The same degree of predictability does not hold true relative to cattle and swine distribution because of the variable economic factors that affect their production. The investigator can, however, by studying these maps, determine which regions are likely to be best adapted to animal production. Some additional values and uses of these maps include studies to show the relation of the yield of a crop to soil regions; studies to indicate effects of climate and weather condition upon yields ; studies to show the distribution of livestock in relation to grain, pasturage and hay crops; and possiblv studies to indicate changes which occur in density of production of livestock with respect to economic conditions . In order to make the maps more meaningful and to know the reliability of them, the data may be used in working out the probable error of the medians. For example, using corn in Fillmore County, the P. E. (Probable Error) of median is 1.8 bushels, which interpreted means that the chances aie even (50-50) that the yield will be within 1.8 bushels of the median (25 bushels) or between 23.2 and 26.8 bushels per acre. The .P. E is 0.9 bushels for wheat in Fillmore, which means that the chances are even (SOSO ) that the yield will be within 0.9 of a bushel of the median (16.4 bushels ) or between 15.5 and 17.3 bushels per acre. Limitations in studies of this kind include the short period of time that records have been kept; errors in obtaining data; and in some cases faulty estimation of yields. The Physiographic Expression of the Indian Creek Plutons of the Denver Mountain Parks Region, Colorado MARGARET FXTLLER BOOS University of Denver The physiographic pattern of the Denver Mountain Parks area, fifteen to twenty miles west of Denver, Colorado , is developed over schist and ranks of granite plutons in en echelon pattern having striking structural and topographic trends from northwest to southeast. The granite plutons stand out as lumpy granite mountains which have oversteepened southeast faces and long smooth heavily timbered northwest slopes. Granite dikes form low ridges and festoons of little elevations which link the plutons and emphasize the northwest to southwest topographic lines. The schist into which the granite is intruded is a relatively weak rock and underlies the valleys and the flattish "parks" common to the area. The entire upland of the Denver Mountain Parks region lies seven to eight thousand feet above sea level. Major streams are antecedent to the present topography and are adjusted around the granite plutons and mostly flow eastward through canyons five hundred to a thousand feet deep debouching from the mountain areas into the foothills region at about six thousand feet a. t. Subsequent and consequent tributaries have a trellised pattern such as is developed in folded beds of sedimentary rock, but here the bedrock is alternating weak beds of schist and strings of strong granite dikes and elongate plutons, with well developed northwest to southeast trends. The geomorphology of schist and granite has influenced settlement patterns . Mountain ranches which produce oats and potatoes, lettuce and (30) peas and wild hay occupy the heads of subparallel valleys in the schist. Summer homes of Denver people and tourist cottages fill the "parks" and are concentrated on the southwest sides of granite mountains and ridges. North and northeast facing slopes are mostly timbered and lumber mills are numerous in the heads of the northwest facing valleys. The Structure of Summer Wind Over San Juan Island, Washington OAROL O. BEAMER University of Washington, Seattle, Washington This paper is the result of the first of a series of experiments being conducted at the University of Washington Océanographie Laboratories, Friday Harbor, San -Juan Island, upon the problem of summer wind structure over San Juan Island, under the direction of Dr, Phil E. Church...