When we threw some large stones into the pipe, the steam instantly carried them up to an amazing height; and in several instances, when they went up quite perpendicularly, kept them within its influence for some minutes, throwing them upwards several times successively, in a very strange manner; the Geyser seemed to play with them as a boy plays with his ball when he throws it up and catches it again and again. We were not yet satisfied, because we had not seen an eruption fairly from beginning to end; so we waited some time longer. At about seven o'clock in the morning, we heard low grumbling sounds near the great Geyser, and the water in the basin bubbled up a little more actively. We then had an hour and a half of anxious expectation, during which we kept walking round the hillock; there were then about a dozen loud reports which made the earth tremble, and the water rose to near the top of the basin, and became so restless that many of the waves washed over the edge. A little while afterwards, the reports became as loud as the firing of artillery; the ground shook violently under our feet; we ran down the mound, and had hardly got upon the level ground before the water rushed up the pipe with such thick clouds of steam, as completely to conceal the stream. These bursts took place in this manner to the height of about twenty feet. There was then a rest for a few seconds, which was followed by several jets from forty to sixty feet high; and after them a column was thrown up eighty feet high, and ten feet in diameter. But the last jet was the most remarkable, for it was more than ninety feet high, and lasted for seven minutes. This great effort seemed to have wearied the Geyser, for the water instantly sunk down out of the basin into the pipe, quite out of sight; but in a few minutes it rose again to within a foot of the edge of the basin, and then remained stationary. Besides the great perpendicular jets, there were many little ones curling and twisting about in all directions; and we were taught to be careful of these by one of my companions getting badly scalded in the leg, for they were very sudden and uncertain in their movements. When we were quite sure it was all over, we tried the temperature of the water in the basin, and found it to be twenty degrees cooler than before the eruption, which was probably caused by the exposure of the water which had been thrown up into the air. It seems there are generally about five or six eruptions of each of the two great Geysers, within twenty-four hours. But while we were on the spot, many of the smaller springs spouted up much oftener, and one bustling little thing darted out its waters in all directions, three or four times in an hour.