You mean the ice sheet that covered the land that I am now typing this reply from?
VANISHED GLACIERS
I would gladly have explored the main trunk of this beautiful basin, from the highest snows upon the divide of the Tuolumne, to its mouth in the Merced Cañon below Yosemite, but alas! I had not sufficient bread, besides I felt sure that I should also have to explore the Tamarac basin, and, following westward among the fainter, most changed, and covered glacier pathways, I might probably be called as far as the end of the Pilot Peak Ridge. Therefore, I concluded to leave those lower chapters for future lessons, and go on with the easier Yosemite pages which I had already begun.
But before taking leave of those lower streams let me distinctly state, that in my opinion future investigation will uncover proofs of the existence in the earlier ages of Sierra Nevada ice, of vast glaciers which flowed to the very foot of the range. Already it is clear that all of the upper basins were filled with ice so deep and universal that but few of the highest crests and ridges were sufficiently great to separate it into individual glaciers, many of the highest mountains having been flowed over and rounded like the boulders in a river. Glaciers poured into Yosemite by every one of its cañons, and at a comparatively recent period of its history its northern wall, with perhaps the single exception of the crest of Eagle Cliff, was covered by one unbroken flow of ice, the several glaciers having united before they reached the wall.
September 30th—Last evening I was camped in a small round glacier meadow, at the head of the easternmost tributary of the cascade. The meadow was velvet with grass, and circled with the most beautiful of all the coniferae, the Williamson spruce. I built a great fire, and the daisies of the sod rayed as if conscious of a sun. As I lay on my back, feeling the presence of the trees-gleaming upon the dark, and gushing with life—coming closer and closer about me, and saw the small round sky coming down with its stars to dome my trees, I said, “Never was mountain mansion more beautiful, more spiritual; never was moral wanderer more blessedly homed.'’ When the sun rose, my charmed walls were taken down, the trees returned to the common fund of the forest, and my little sky fused back into the measureless blue. I was left upon common ground to follow my glacial labor.
http://www.yosemite.ca.us/john_muir_writings/yosemite_glaciers.html