Where morainal débris covers thousands of acres, it is probable that valuable mineral veins were in some cases covered, prospecting prevented, and mineral wealth lost; but on the other hand, the erosion done by the glacier, often cutting down several hundred feet, has in many cases uncovered leads which otherwise probably would have been left buried beyond search. Then, too, millions of dollars of placer gold have been washed from moraines. In addition to the work of making and giving the mountains flowing lines of beauty, the glaciers added inconceivably to the richness of the earth's resources by creating vast estates of soil. It is probable that glaciers have supplied one half of the productive areas of the earth with soil; the mills of the glaciers have ground as much rock-flour--soil--for the earth as wind, frost, heat, and rain,--all the weathering forces. This flour and other coarser glacial grindings were quickly changed by the chemistry of Nature into plant-food,--the staff of life for forests and flowers. Glaciers have not only ground the soil but in many places have carried this and spread it out hundreds of miles from the place where the original raw rocks were obtained. Wind and water have done an enormous amount of work sorting out the soil in moraines and, leaving the boulders behind, this soil was scattered and sifted far and wide to feed the hungry plant-life. At last the Glacial Winter ended, and each year more snow melted and evaporated than fell. Snow-line retreated up the slopes and finally became broken, even in the heights. To-day, in the Rockies, there are only a dozen or so small glaciers, mere fragments of the once great ice cap which originally covered deeply all the higher places and slopes, and extended unbroken for hundreds of miles, pierced strangely with a few sharp peaks. The small remaining glaciers in the Rocky Mountains lie in sheltered basins or cirques in the summits and mostly above the altitude of thirteen thousand feet. These are built and supplied by the winds which carry and sweep snow to them from off thousands of acres of treeless, barren summits. The present climate of these mountains is very different from what it was ages ago. Then for a time the annual snowfall was extremely heavy. Each year the sun and the wind removed only a part of the snow which fell during the year. This icy remainder was added to the left-over of preceding years until the accumulation was of vast depth and weight. On the summit slopes this snow appears to have been from a few hundred to a few thousand feet deep. Softened from the saturation of melting and compressed from its own weight, it became a stratum of ice. This overlay the summit of the main ranges, and was pierced by only a few of the higher, sharper peaks which were sufficiently steep to be stripped of snow by snowslides and the wind.