326 T. A. Jaggar— Conditions affecting Geyser Eruption. 



as follows : capacity of each flask, one quart ; length of main 

 geyser tube 4 feet, diameter (outside) T 5 ¥ inches : diameter of 

 basin 2 feet; the bottom flares funnel-wise from the center 

 slightly, and is provided with a J inch outlet tube t. The 

 lower flask rests on a sheet of wire-netting over the flame of a 

 four- or six-tube Bunsen burner, and the basin and reservoir 

 bottle are supported above on a wooden frame. The basin is 

 of zinc and may be raised or lowered so that the mouth of the 

 geyser tube is flush with the bottom of the basin or raised 

 above it as shown. The supply tube is recurved slightly at the 

 bottom of the flask, so that the cold jets which siphon in from 

 the reservoir will not be directed against the glass wall of the 

 flask and break it. The reservoir bottle is connected by rub- 

 ber tubing with the supply tube, so that the bottle may be 

 freely raised or lowered to various levels indicated by the 

 dotted lines a, b and o. 



Experiment 1. " Old Faithful " Type. 



When heat is applied below T , the reservoir level being at a, 

 after about 14 minutes an eruption takes place, characterized 

 by violent ebullition in the flask below, ejection of the water- 

 column to a height of about 4 feet and of a mixture of steam 

 and water for a few seconds longer : then the water-level in 

 the reservoir is seen to fall suddenly, a stream is seen to be 

 flowing into the lower flask from the curved tip of the supply- 

 tube, the cooling of the base of the column is accompanied by 

 condensation of steam and downward suction, the water rises 

 to level a again and a period of repose follows. It should 

 be noted that if the level of the cooler water in the reservoir 

 is at a, the expanded warmer water in the geyser tube is some- 

 what above a. The process described is repeated at regular 

 intervals of about 1^ minutes, the duration of each eruption 

 being about 20 seconds. If the water in the reservoir be not 

 renewed it gradually becomes warmer and the intervals are of 

 shorter duration. In this case, or with the reservoir level 

 somewhat higher, as at 5, and the geyser mouth raised above 

 the basin as shown in the figure, we have in miniature the con- 

 ditions of " Old Faithful." " 



Experiment 2. " Excelsior " Type. 



The conditions are altered if we raise the reservoir level to 

 the point shown in the figure, namely, just above the height of 

 the geyser mouth (c). In such case there is continuous over- 

 flow of the hot water, and if the outlet tube t be left open, 

 this will continually flow off: this overflow must be constantly 

 compensated at the supply tube by cooler water from the reser- 



