"The Castle Geyser differs from Old Faithful and the Bee Hive mainly in the fact that it has a long steam period, during which the steam pours out or is pushed from the geyser throat with great violence and a terrific noise. There appear to be only two possible explanations of this difference, viz., either an accumulation of immense volumes of steam in the Castle, or an instantaneous formation of steam throughout the length of the geyser tube. The former, to our mind, is untenable, because it seems impossible that the water, which is exhausted in fifteen minutes, should exert enough power to keep down the immense amount of steam that escapes for more than an hour. According to Bunsen's theory, it can be readily explained. The relief afforded by the first part of the eruptions allows the superheated water to rise rapidly, and before it can reach the top or orifice of the tube it is all converted into steam from the top downward with inconceivable rapidity, and must be forced out with the terrific violence which is noted in the case of the Castle. On page 208 we have expressed the opinion that it is the oldest geyser in the region, and it seems to us that a greater length in the tube, with a consequent greater supply of water, will account for the difference between the Castle and Old Faithful, the latter of which we consider one of the youngest geysers in the Upper Geyser Basin." A study of the Caves in connection with the active Geysers indicates that the theory he suggests and then rejects, is probably the true explanation of the difference between the two kinds of geysers. It seems that the length of the tube must necessarily have more effect on the height of the jet than on the generation of steam; as after an eruption the tube is hotter than at any other time and therefore the generation of steam in it should be less than usual, unless the fresh inflow of water was cold. Then if the storage cavities are broad but low, the steam cannot accumulate above the water; but when the pressure becomes sufficient to force a passage through the tube, the water and steam are expelled together until the pressure is exhausted. But if the storage chambers are vertical fissures, as Wind Cave illustrates, vast quantities of steam must accumulate above the water level in the main reservoirs before the pressure can become sufficient to expel the water in the tube, after which steam alone continues to rush out until the pressure is so relieved that it can no longer force a passage through the water remaining in the trap, when quiet is restored. By the constant addition of fresh water from the surface, by percolation or other usual ways of sinking, the necessary conditions for the generation of steam are maintained with surprising regularity.