A PECULIAR PROCESS OF SULPHUR DEPOSITION 807 



called Ponto. This small lake is 210 meters in diameter and occu- 

 pies an explosion crater. When this is quiescent, the depth of the 

 lake is from 30 to 35 meters in the center, but during periods of 

 activity it is 30 meters deeper. Toward the margins the lake 

 becomes abruptly shallower, as shown in Fig. 2. 



The water of the lake is strongly acidic, and has a temperature 

 of 40 C. Around the margins, through innumerable small fis- 

 sures, sulphur is deposited, and the country rock is strongly impreg- 

 nated with it. That the fissures extend beneath the surface of 

 the water is clearly shown by the bubbles of gas which rise to the 

 surface of the lake in various places. The amount of gas emitted 

 is ordinarily not very great, but during periods of low barometric 

 pressure enormous quantities escape. Not only do the fissures 

 emit gas, but the conduit of the 

 crater itself is active, and during 

 the months of February, June, 

 July, and August, when the 

 barometer is low in this vicinity, 



CU>. f\ \t ■ a~ tHifTm 



periodic eruptions of hot water FlG 2 ._ Profile of Lake Ponto and 



and gas take place. Lake Ichibishinai. 



During the writer's visit to 

 this locality in August, 191 2, paroxysmal eruptions of gas and 

 water were noticed near the center of the lake at intervals 

 of from one to three hours, and whenever the bubbling began 

 workmen rowed to the spot. By means of a pulley attached 

 to a framework resting upon two boats, the men lowered a 

 cylindrical iron bucket, with a capacity of about 140 liters, in the 

 center of the bubbling area to the bottom of the lake. When 

 the bucket was withdrawn, it was practically filled with sulphur 

 grains which were formed by the union of the gases with the water 

 in the lower part of the conduit. Being specifically heavier than 

 water, the sulphur grains, forced upward by the ebullition, sank 

 toward the bottom and into the bucket. In this manner, while 

 the crater is active, a hundred buckets of sulphur are easily brought 

 up in a day. 



The greater part of the sulphur is dark gray in color, but some 

 is yellow. The grains are hemispherical, oval, kidney-, fig-, or 



