36 Transactions. — Miscellaneous. 



and being served out again tlirougli the many springs occuri'ing on the road to 

 the Whau (the Western Springs), at Onehunga beach, Lake Takapuna, and 

 other places. These springs are merely the overflow of what is a natural 

 subterranean reservoir. To prove this, one must consider how volcanic rocks 

 occur, especially those at Mount Eden and its vicinity, and their physical 

 construction. 



Dr. Hochstetter remarks about these volcanoes that " the first outbursts, 

 as a closer observation shows, were probably submarine ; they took place at 

 the bottom of a shallow, muddy bay, little exposed to waves and wind, and 

 consisted of flowing mud mixed with loose masses, such as fragments of sand- 

 stone and shale, lava debris, cinders, and scoria {Jajnlli), which now form beds 

 of volcanic agglomerate or tuff. Tlie ei'uptions occurred, no doubt, at intervals, 

 for in this manner alone can the fact be accounted for that the ejected 

 material has been deposited round the point of eruption in layers one above 

 the other, forming low hills gradually rising, and with a circular basin or dish- 

 shaped crater in the middle ; a cross section presents clearly the diffei-ent 

 layers whicli usually slope inwards towards the bottom of the crater, as well 

 as outwards down the sides." Further on, he says : — " A complete volcanic 

 system accordingly consists of three pai-ts : a tuff cone the base and pedestal of 

 the whole frame, a lava cone, the chief mass of the mountain, and a scoria or 

 cinder cone forming the top, with the crater." 



These violent outbursts and ejection of such large qiiantities of scoria and 

 lava would undoubtedly produce very important effects on the surrounding 

 country and on the rocks immediately below and through which the eruptions 

 occurred. Before a vent could have been made througli the earth's crust, it 

 must have been somewhat upheaved and cracked to emit the molten materials 

 below, which, as they ascended, would have enabled the crust to subside, and 

 this it would continue to do as long as material was ejected, for the earth's 

 crust, by its own weight and that of the piled-up scoria and lava above, would 

 necessarily sink down and occupy, in a measure, the place of the ejected 

 materials. Thus, below a volcanic mountain of any considerable extent, there 

 must be a basin-like depression immediately beneath capable of holding a 

 large quantity of water, which, combined with the water in the mountain 

 above, retained in it as if it were a large sponge, may probablv be made 

 available for a water supply. But as the quantity in the basin and above it 

 may be inadequate for a large supply, we must consider whether this may be 

 helped by the adjacent waters stoi-ed up all around. An inspection of lava 

 and scoria beds prove that they are able to hold a large amount of water from 

 their porosity, dependent upon the amount of resistance to dam the waters 

 back. 



Before it can be decided whether a sufficient quantity of water could be 



