424 EEPORT UNITED STATES GEOLOGICAL SURVEY. 



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 2US we have exi)ressed 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 Uijper 

 Geyser Basin (see page 221). 



When we attempt to explain the differences between classes 3 and 4 

 and 1 and 2, i. e., between those geysers that have a. single water erup- 

 tion and those that have several periods or phases in each eruption, we 

 meet with greater dlfiiculties. It msbj be partially explained by assum- 

 ing that there are several reservoirs from which the water is supplied to 

 the geyser tube. These reservoirs must be quickly emptied into the 

 geyser tube and slowly refilled to exj^lain the action, and here some 

 modification of McKenzie's idea may be the true one. The water in 

 these supposed reservoirs must be in such thermic condition that a com- 

 paratively short time in the actual geyser tube is sufficient for the pro- 

 duction of the necessary conditions for an eruption. 



Irregularities in the size and shape of the geyser tube leading to the 

 basin or bowl at the surface must necessarily have considerable influence 

 on the eruptions. In a j)erfectly straight tube there would not be apt to 

 be as great differences in the temperatures of the different parts of the 

 tubes as in one which was very irregular. The form of the crater or bowl 

 seems to modify but little, if any, the action of the geysers, except as to 

 the form of the column or mass of water thrown up into the air. In 

 those cases like the Giantess, where the bowl contains a large mass of 

 water, of course there is more resistance to the escape of the lower layers 

 in which the geyseric action is occurring. We can readily see how the 

 appearance of the ejected mass of water would thus depend, to a great 

 extent, upon the character of the containing bowl, while the effect upon 

 the phenomena occurring in the subterranean passages would be slight. 

 AVe can imagine its having some effect upon the length of the intervals, 

 but the fact remains that a geyser may consist of a simple tube, as in 

 the Bee Hive, or a tube with an expanded basin at the top, as in the 

 Grand, Old Faithful, &c., or as an immense reservoir of water above a 

 tube, as seen in the case of the Excelsior, Giantess, Oblong, and others. 



CHAPTER XII. 



Influences modifying Geysers. 

 EFFECT OF THE ATMOSPHERE UPON GEYSERS. 



In New Zealand, when the springs were first discovered, the natives 

 frequently referred to the effect of tlie atmosphere upon the action of 

 the geysers. One of them they called Tapui (wind pointer). 



Capt. Gilbert Mair sjient four years (1870-1874) taking observations 

 in the Eotorua District. Ide notes that the springs are undoubtedly 

 affected by the state of the atmosphere, and during the time mentioned 

 above found no deviation.* 



* On the lufltieuce of Atmospheric Changes on the Hot Springs and Geysers in the 

 Rotorua District, by Capt. Gilbert Mair, New Zealand Trans. Inst., vol ik, 1876, pp. 

 22-29. 



