Hitherto, when not travelling on the ice, we had to make our way over snow seldom less than two feet deep, but as we reached the base of the mountains it suddenly disappeared.  As far as we could see to the eastward, not a patch was visible.  Had it not been for the frozen rivers and the leafless trees, we might have fancied that summer was returning.  This phenomenon occurs along the whole base of the Rocky Mountains, where there is a belt of nearly twenty miles in width perfectly free from snow.