402 Transactions .—Geology . 



ville 82ffc. ; whilst at the Tauph-i Gorge the elevation is only 

 39ft. Yet; we find that the Waikato cai'ried its alluvium to 

 the Eotorangi Swamps, eight miles in a southerly direction, 

 against the present grade of the country, the natural fall being 

 north and east, towards Morrinsville and Taupiri, at the rate 

 of 7ft. to the mile. It becomes at once evident, on consider- 

 ing the relative heights of the land in the middle basin, that 

 it never could have been occupied by a lake, nor could these 

 deposits have been laid by the Waikato at all if the levels of 

 the country were as we now find them. The lake would have 

 four outlets : one at Morrinsville, one at Hapuakohe, one at 

 Matahura, and the present river-bed through the Taupiri 

 Gorge (supposing it to have existed at that time), all con- 

 siderably below the bed of the lake. It maybe suggested that 

 the deposits are estuarine, and were laid when the middle 

 basin was a bay of the sea. The whole topography of the 

 country and the character of the alluvium are against this 

 theory. There is no trace of marine deposits to be found, and 

 if any existed they would easily be discovered amongst the 

 detritus which is scored and exposed by the streams, fre- 

 quently to great depths, all over the plain. Neither is there 

 any trace of a sea-beach found fringing the swamps round the 

 clay-hills in the plain which were islands dotting the lake. 

 Hochstetter says of the Middle Waikato basin: "The whole 

 basin was, previous to the last elevation of the North Island, 

 a bay of the sea, extending from the Hauraki Gulf far into the 

 interior. The steep margins of the surrounding hills coTitinue 

 to this day displaying the seashore of old, and the singular 

 terrace formation on the declivities of the hills and the river- 

 banks within the basin is the result of a slow and periodical 

 upheaving." This being so, as the land gradually rose and 

 the sea receded, tidal channels would have been left within 

 the estuary, through which tlie rivers and streams would con- 

 tinue to flow out of the basin to the sea in the Hauraki Gulf — 

 that is, if no change of the surface took place to prevent the 

 natural course. We now find, however, that the valleys 

 where these estuarine channels might be looked for are filled 

 with an alluvial deposit of the detritus of the volcanic country 

 brought down by the Waikato Eiver, and placed in stratified 

 horizontal beds, as they could only be laid in very slowly- 

 moving or impounded water. 



The depth of these deposits varies considerably. In the 

 Eukuhia Swamp, between Hamilton and Ohaupo, they are 

 from 50ft. to 70ft. ; in the Piako Swamp, from 40ft. to 60ft. ; 

 at Hamilton, from 40ft. to 70ft. ; and in the neighbourhood 

 of Taupiri, the lowest point in the basin, it is a remarkable 

 fact that the deposit is lightest. Beneath the deposit in 

 many parts of the basin the old land-surface may be seen. 



