THE GEYSERS AT ROTORUA. 207 



140deg. minimum to 180deg. maximum. I thought that this increased 

 activity of the springs, when the water was hot, was owing to the 

 difference in the specific gravity between hot and cold water which the 

 spring tube or fissure might contain in its column, and that this diffe- 

 rence might be sufficient to cause the water to rise a foot or two above 

 present level according to the depth at which this influence (in the 

 temperature of the water) would take place. I had some temporary 

 works carried out to prove the correctness of this theory, and to my 

 delight found that it was quite true, and that instead of a small rise of 

 two feet, which would have been quite sufficient for our purpose, there 

 was force enough in the springs under these altered circumstances to 

 ' form geysers. Having further acquired the knowledge that the whole 

 of the springs in the Oruawhata and Chameleon basins were hydros ta- 

 tically connected, I arranged a system of pipes over the three principal 

 springs, connecting each of them by secondary pipes to three valves by 

 means of which either of the springs can be made to play as a geyser at 

 will. To keep the springs quiet, low, and cool during the time the 

 works were being carried out, cold water from the town main was 

 injected into one of the three spring tubes, pumping it with an ejector 

 out of another, whilst the work of cementing the geyser tube was going 

 on in the third ; and by shifting the injector and ejector pipe from one 

 spring tube to the other I had the three geyser tubes firmly secured. 

 These works were [finished early in May, 1890 ; and the springs were 

 thus kept quiescent for three weeks to allow the concrete to set 

 properly, and eventually four days longer, so as to start them into 

 action for the first time on the Queen's Birthday, at two p.m. A con- 

 siderable number of people gathered to see this novel experiment. The 

 new fountains were christened the "Malfroy's Group of Geysers," their 

 distinctive names being the "Victoria," the "Nelly," and the "May." 

 [The geyser action in different springs was then described, and it was 

 shown how it could be induced.] From the experience thus gained I 

 support the theory that the geyser tubes are connected with subter- 

 ranean caverns or chambers, and that heat or superheated steam pene- 

 trating through fissures s applies the natural or motive force, and I 

 conclude that the difference between the specific gravity of hot and cold 

 water within the geyser tube will thus produce every phenomenon of 

 geyser action to be observed at Rotorua, and I am led to believe that, 

 by studying the action of geysers and springs in this district, they could 

 in most cases and to a certain extent be regulated and controlled. 



Geyser action may be briefly explained according to the foregoing. 

 Supposing that an even-sized tube full of water become so hot that 

 steam generated at the bottom, under heavy pressure, rises through it 

 without being condensed, there comes a time when several globules of 

 this steam will be in the tube at the same time, and as they rise to the 

 surface they will expand in proportion to the release of pressure exerted 

 upon them, and when coming near the surface they, as it were, explode, 

 throwing the small quantity of water contained in the tube above them 

 into the air, forming irregular intermittent explosions. Eruptions of 

 longer duration can be explained thus : The actual weight of water in 

 the geyser tube, acting as valve on the force, may by means of these 

 globule explosions, Grid itself suddenly released by, say, half the pressure 

 of the column of water. The equilibrium being thus destroyed, the 



