Glaciers the world over have been the chief makers of lake-basins, large and small. These basins were formed in darkness, and hundreds and even thousands of years may have been required for the ice to carve and set the gems whose presence now adds so much to the light and beauty of the rugged mountain-ranges. The ponderous glaciers or ice rivers in descending from the mountain-summits came down steep slopes or precipitous walls and bore irresistibly against the bottom. The vast weight of these embankments of ice moving almost end-on, mixed with boulders, tore and wore excavations into the solid rock at the bottom of each high, steep descent. Nature's ways are interestingly complicated. Both the number and the location of many of these glacier lakes are due in part to the prevailing direction of the wind during the last glacial epoch. This is especially true of those in the Snowy Range of the Rocky Mountains, which fronts the Great Plains. The majority of the lakes in this range are situated on its eastern slope. Westerly winds undoubtedly prevailed on these mountains during the depositing of the snows which formed and maintained the glaciers that excavated these lake-basins. As a result, much of the snow which fell on the summit and its westerly slope was swept across and deposited on the eastern slope, thus producing on the eastern side deeper ice, more glaciers, and more appreciable erosion from the glaciers. The eastern summit of this range is precipitous and is deeply cut by numerous ice-worn cirques which extend at right angles to the trend of this range. These cirques frequently lie close together, separated by a thin precipitous wall, or ridge. On the westerly side of the range the upper slopes descend into the lowlands through slopes and ridges rounded and but little broken. Over these it is possible to ride a horse to the summit, while foot travel and careful climbing over precipitous rocky walls is in most places required to gain the summit from the east. Westerly winds still blow strongly, sometimes for weeks, and the present scanty snowfall is largely swept from the western slopes and deposited on the eastern side. So far as I know, all the remaining glaciers in the front ranges are on the eastern slope. The Arapahoe, Sprague, Hallett, and Andrews Glaciers and the one on Long's Peak are on the eastern slope. They are but the stubs or remnants of large glaciers, and their presence is due in part to the deep, cool cirques cut out by the former ice-flows, and in part to the snows swept to them by prevailing westerly winds.