206 JOURNAL OF SCIENCE. 



September, 1888, I built a temporary wall directing the Waikoroihi 

 water away from the " blue pool." This soon had the effect of raising 

 the temperature of the blue pool from 200° to 210 s Fahr. The water 

 rose a few feet and began to boil furiously, then the pipe, which I 

 call the " Indicator," became active, and as soon as this took place the 

 water in the " blue pool " would cease boiling and go down again to the 

 low water-line. I watched this same action for several hours, but 

 unless the water of the blue pool rose to the level of the overflow drain 

 there was no ei'uption of Pohutu. Seeing that this small indicator 

 tube acted as a kind of safety valve I tried to close it up with bags, 

 stones, etc., bixt failed, the steam and water finding its way through 

 small fissures in the rocks. It then occurred to me to build a kind of 

 dam around the " indicator " so as to collect the water ejected by it, 

 and also lead some of the water from "Waikoroihi into this dam, thus 

 causing this cooled water to flow back down the indicator tube. This 

 had the desired effect. The indicator stopped playing altogether as 

 long as I could keep a small stream of cooled water running down it. 



On the following day Waikoroihi stopped playing. The water of 

 the blue pool rose to the level of the overflow drain, became more and 

 more active, and on the 9th of September, two days after the works 

 were finished, Pohutu gave a grand eruption, lasting nearly two hours, 

 throwing large volumes of water from 60 to 80 feet high. This 

 eruption was repeated in the evening, and from that date till December, 

 1889, it played regularly about twice in 24 hours. During this time, 

 while I was acting as commissioner at the Paris Exhibition, there was 

 no one on the spot to look after these special works. The consequence 

 was that Pohutu again stopped playing regularly. On my return, in 

 February, 1890, I was informed that Pohutu had not played or been 

 in active eruption for the last nine weeks. I at once went over to see 

 it, and finding that the works I had made had been tampered with, I 

 had them put into temporary repair, with the result that Pohutu played 

 wp again a few hours after the work was finished, and its action has 

 continued ever since, though not so regularly as before, but this is no 

 doubt only due to the defective repairs of former walls, etc. 



As a further illustration of what may be done in regulating the 

 action of geysers, or even in creating or starting new ones, I may state 

 that in the sanatorium grounds there are two hot springs with concrete 

 basins around them, which were never known to have geyser action, 

 though the formation of the surrounding rocks shows that they had 

 been geysers at some remote period. These springs supply the hot 

 swimming bath, but during the year 1889, they had gone so low, and 

 were so much influenced by the atmospheric pressure, that sometimes 

 they would remain for several clays two or three inches below the level 

 of the outflow pipe, thus discharging no water. This became a matter 

 of great importance, as the bath which cost £1,000 threatened to 

 become useless, owing to not being able to keep it at a proper and 

 regular temperature. 



It occurred to me that by contracting the springs proper into pipes, 

 it would prevent the hot water from becoming cold, by admixture with 

 the water in the basin, for I had noticed that when the springs were 

 active, the temperature of the water in the basins would rise from 



