The first persons who found it in their way to pay more than a tourist's visit to this interesting object were Rev. J. L. Patton, Mr. Prentiss Baldwin, and myself, who spent the entire month of August, 1886, encamped at the foot of the glacier, conducting such observations upon it as weather and equipment permitted. From that time till the summer of 1890 no one else stopped off from the tourist steamers to bestow any special study upon it. But during this latter season Mr. Muir returned to the scene of his discovered wonder, and spent some weeks in exploring the interior of the great ice-field. During the same season, also, Professors H. F. Reid and H. Cushing, with a well-equipped party of young men, spent two months or more in the same field, conducting observations and experiments, of various kinds, relating to the extent, the motion, and the general behaviour of the vast mass of moving ice. [Illustration: Fig. 13.--Shows central part of the front of Muir Glacier one half mile distant. Near the lower left hand corner the ice is seen one mile distant resting for about one half mile on gravel which it had overrun. The ice is now retreating in the channel. (From photograph.)] The main body of the Muir Glacier occupies a vast amphitheatre, with diameters ranging from thirty to forty miles, and covers an area of about one thousand square miles. From one of the low mountains near its mouth I could count twenty-six tributary glaciers which came together and became confluent in the main stream of ice. Nine medial moraines marked the continued course of as many main branches, which becoming united formed the grand trunk of the glacier. Numerous rocky eminences also projected above the surface of the ice, like islands in the sea, corresponding to what are called "_nunataks_" in Greenland. The force of the ice against the upper side of these rocky prominences is such as to push it in great masses above the surrounding level, after the analogy of waves which dash themselves into foam against similar obstructions. In front of the _nunataks_ there is uniformly a depression, like the eddies which appear in the current below obstacles in running water.