taken at the height of its play
by F. Jay Haynes, then official photographer of the park.

"The first photographs I made were in the fall of 1881," Mr. Haynes
writes me. "The eruptions continued during the winter at increasing
intervals from two hours, when the series began, to four hours when it
ceased operations before the tourist season of 1882. Not having the
modern photographic plates for instantaneous work in 1881, it was
impossible to secure instantaneous views then, but in the spring of
1888, I made the view which you write about. It was taken at the fulness
of its eruption.

"The explosion was preceded by a rapid filling of the crater and a great
overflow of water. The column was about fifty feet wide and came from
the centre of the crater. Pieces of formation were torn loose and were
thrown out during each eruption; large quantities eventually were
removed from the crater, thus enlarging it to its present size."

Here we have a witness's description of the process which clouds the
career of the Excelsior Geyser. The enlargement of the vent eventually
gave unrestrained passage to the imprisoned steam. The geyser ceased to
play. To-day the Excelsior Spring is one of the largest hot springs in
the Yellowstone and the world; its output of steaming water is constant
and voluminous. Thus again we find relationship between the hot spring
and the geyser; it is apparent that the same vent, except perhaps for
differences of internal shaping, might serve for both. It was the
removal of restraining walls which changed the Excelsior Geyser to the
Excelsior Spring.

For many years geyser action remained a mystery balanced among
conflicting theories, of which at last Bunsen's won general acceptance.
Spring waters, or surface waters seeping through porous lavas, gather
thousands of feet below the surface in some pocket located in strata
which internal pressures still keep hot. Boiling as they gather, the
waters rise till they fill the long vent-hole to the surface. Still the
steam keeps making in the deep pocket, where it is held down by the
weight of the water in the vent above. As it accumulates this steam
compresses more and more. The result is inevitable. There comes a moment
when the expansive power of the compressed steam overcomes the weight
above. Explosion follows. The steam, expanding now with violence, drives
the water up the vent and out; nor is it satisfied until the vent is
emptied.

Upon the surface, as t