Fig. 3. — Forms of sulphur grains 



808 Y. OINOUYE 



spindle-shaped (Fig. 3), and they are usually about o. 2 to 3 . o mm. 

 in diameter. The grains are not solid, but hollow, and the cell 

 walls, which are usually rough on the outside on account of a coat- 

 ing of impurities and of very minute sulphur particles, are so thin 

 that they are very easily broken. In fact, many of the larger 

 grains are broken by mutual impact in the water. In the flat side 



of many of the hemispherical 

 forms or at one end of those 

 that are round there is a small 

 hole, which was made by the 

 exit of the gases which remained 

 within it after it was formed. 

 Most of the grains are brought 

 up as distinct individuals, but in some cases they are united in 

 large botyroidal masses. On account of their thin shells, they 

 cannot keep their original forms if even slight pressure is applied, 

 and the sunshine also destroys them. 



Two modes of origin of the sulphur in solfataras have been 

 suggested by geologists and chemists : first, the oxidation of hydro- 

 gen sulphide, probably according to the equation 



2 H 2 S+O i =2H 2 0+ 25, 



secondly, the mutual reaction of hydrogen sulphide and sulphur 

 dioxide, according to the equation 



2 H 2 S+S0 2 = 35+ 2H 2 0. 



The hydrogen sulphide and sulphur dioxide, emanating from 

 the conduit, form numberless bubbles in the lake, and where they 

 are in contact with the water the sulphur is deposited. Thus, 

 layer after layer of sulphur may accumulate in a lake and bedded 

 deposits be formed. 



Similar oolitic sulphur grains are being formed at the present 

 time in the crater lakes of Shirane 1 and Noboribetsu, but they are 

 not being worked. 



'H. Kawasaki, Jour. Tokyo Geol. Society, No. 122. 



