BY R C. RINGROSE, M.A. 61 



I'here is nothing extraordinary in finding a volcanic 

 vent carved out of rock of a much older series. But it 

 is not usual to find them in a condition much the same 

 as when they were in their original state of activity, and 

 unfilled by rock originally being rising columns of lava, 

 or by falUng debris and rocks, either hurled up the chimney 

 itself and falHng back into it, or from surrounding rocks 

 shattered from explosions of steam and gases. There 

 IS no great quantity of debris found immediately round 

 the Crater near Herberton. Denudation, no doubt, has 

 worn away some of the volcanic deposits. But it is likely 

 enough that volcanic ashes were ejected in large quantities 

 with great force over a wide area. That the early flows 

 of basalt broke through the underlying deep-seated rocks 

 with great force is illustrated by the fact that a dyke of 

 basalt, having no visible connections, has been exposed 

 in solid porphyry country rock in one of the cuttings of 

 the Herberton- Evelyn line near the great Northern Gully, 

 in the town of Herberton, showing that the dykes burst 

 through the most solid country rocks apparently from great 

 depths. This is the only known instance of an isolated 

 basalt dyke unconnected with ordinary basaltic outpour- 

 ings, and evidently of the most deep-seated origin. 



The conclusions to be drawn from the observed facts 

 •of the Crater may be : — 



1. That the Crater is a volcanic vent, which is newei 

 than the massive porphyries, and newer than the elvan 

 series, and that all the facts point to its origin being caused 

 Isy a violent manifestation of volcanic activity. 



2. Its origin may be older than the period of the 

 Tertiary Volcanic system. 



3. It must have been a vent for steam gases and 

 volcanic ejecta between the periods of the massive por- 

 phyries, elvan period and the Tertiary volcanic^ period, 



nd it is conceivable that in some early portion of the 



lertiary period, it was an outlet for volcanic bombs of the 



basaltic type, but it has no connection with and may have 



I)een closed up before the period of Lake Eacham and other 



Tertiary volcanoes. 



