Malfkoy. — On Geyser-action at Botorua. 589 



can be absorbed by the discharge of a rather large quantity of 

 water at a comparatively low temperature. 



2. An Intermittent Geyser. — Supposing the action of the 

 hot spring above described to be going on, take the piece of 

 sponge before described (in this case it should be of such a 

 size as to allow about a quarter of the tube to be open) ; in- 

 troduce it into one of the tubes (say C), pushing it well down 

 near the bottom : this will stop part of the cold-water supply. 

 The heat of the spirit-lamp being still the same, the tempera- 

 ture of the water in the flask will rise to the boiling-point due 

 to altitude and pressure; steam, will then form and accumulate 

 in the neck of the flask, and force the water up the tube D, 

 which water will be seen full of small steam-globules as it 

 ascends the tube. These steam-globules, displacing a certain 

 quantity of the water of the tube, naturally reduce the specific 

 gravity of the column of water in the tube D, thereby reducing 

 the pressure exerted on the water in the flask. The water, 

 finding itself released from the pressure, will begin to boil 

 furiously ; large globules of steam mixed with a certain quantity 

 of water will enter and ascend the tube D, and be ejected in 

 the air to a height corresponding with the pressure exerted by 

 the column of cold w'ater contained in the opposite tube C : this 

 furious boiling-action of the water in the flask will continue 

 until such time as the water in the flask is reduced to some 

 considerable distance below the bottom end of the glass tubes, 

 D being then quite empty. Tlie whole of the pent-up force 

 due to the pressure being exhausted, the water in the flask will 

 continue to boil quietly, whilst a small quantity of the cooled 

 water contained in the tray (B) will find its way back into the 

 flask through the tubes C and D, and as soon as the level of 

 the water of the flask reaches the bottom of the glass tubes 

 it will begin to ascend the tube D ; and the pressure thus 

 exerted on the water of the flask will totally stop the boihng- 

 action until such time as the water again acquires the neces- 

 sary temperature to overcome altitude and pressure, when the 

 same action as before described will repeat itself as long as the 

 circumstances remain the same. 



3. A Constant Geyser. — From the foregoing it will readily 

 be understood that, by allowing only a very small quantity 

 of water to find its way down the flask, say through C, and 

 raising the tube D so that it projects above the water in the 

 tray, the action of a constant geyser will be illustrated. 



4. A Fumarole. — If a still smaller quantity of water be 

 allowed in the flask, — in fact, just as much as is consumed in 

 steam, — a steam-jet or fumarole will be produced. 



5. A Mud-volcano. — If a boiling mud-volcano is to be de- 

 monstrated, act the same as for the fumarole, and fix a funnel 

 (see figure, p. 590) full of some soft kind of mud on the top of 



