334 Canadian Record of Science. 



1883.) The frothy and cavernous condition of the sili- 

 ceous sinter of Mount Morgan may be accounted for by 

 the escape of steam while the silica was yet (after depo- 

 sition on the evaporation of the water) in the gelatinous 

 condition so frequently observed in the deposits of hot 

 springs. The aluminous silicates represent the familiar 

 outbursts and Hows of mud. The iron oxide appears to 

 have been deposited in some cases along with the silica 

 and alumina, and in others to have been developed later 

 — its solvent fluid having been, as it were, injected into 

 the interstices and caverns of the silica and alumina. In 

 some cases it may have been originally pyrites, as it now 

 and then occurs in cubical hollows. Calcareous sinter is 

 very common in siliceous springs, and its absence from 

 Mount Morgan must needs imply the local absence of 

 limestones among the rocks from which the spring is fed. 

 The silica would be found abundantly in the quartzites 

 and the alumina in the shale and greywackes of the 

 country rock in the neighbourhood, and possibly both silica 

 and alumina may have come in part from a deep seated 

 underlying granite. The gold, and to some extent the 

 iron, may have been dissolved out of iron pyrites of such 

 reefs as the " Mundic Eeef " seen in Mundic Creek. 



In such active geysers as are accessible to observation, 

 we find a narrow pipe or fissure, terminating upwards in 

 a crater-like cup or basin. The Great Iceland Geyser, for 

 example, has a pipe 12 feet in diameter, which has been 

 sounded to a depth of 70 feet. I have seen no satisfactory 

 explanation of the necessity for a cup, nor can suggest 

 one, but all the same the repeated ocurrence of the cup 

 evidently takes place in obedience to some natural law. 

 It may be taken for granted that the Mount Morgan 

 geyser was no exception to the rule, and I believe that 

 that upper portion of the Mount where ironstone pre- 

 dominates, and to which gold is almost confined, repre- 

 sents a basin occasionally filled with a fluid in which iron, 



