2IO JOURNAL OF SCIENCE. 



sides of the valleys were steep and the hills met the sea, it was 

 impossible for the remains of vegetation to accumulate to any extent, 

 and this explains the somewhat anomalous fact that the coal measures 

 do not always contain coal. The steepness of the land during the coal 

 period is also accountable for the noticeable fact that our coals often 

 thin out towards the clip, and, where lying near the old rocky floor, are 

 usually found to conform with the contours of its surface. 



But whether the forests which formed the coal grew on soils lying 

 directly on the old basement rock, as we find is the case with those of 

 the Auckland provincial district, or on the upper surface of the areas 

 reclaimed from the sea. as is the case of the forests which formed the 

 Shag Point and West Coast coals of the Middle Island, it happened that 

 after a long period of rest, permitting the accumulation of thick deposits 

 of vegetation, the land began to sink slowly, aud in course of time the 

 vegetation became covered by fluviatile clays and sands, generally con- 

 taining fragments of leaves and other plant remains derived from the 

 vegetation which continued to flourish on the higher portions of the dry 

 lands which had not become submerged. 



As the land continued to sink, the fluviatile or estuarine beds 

 became covered by blue clays and greenish- coloured sands containing 

 the embedded remains of the numerous mollusca, crustaceans, corals, 

 whales, sharks, and other life which teemed in the seas of those times. 

 In a few instances in the north of Auckland coalfields, true marine beds 

 containing a varied molluscous life appear close to the roof or upper 

 surface of the coal. It is difficult to look back into these old eocene 

 times, and judge the conditions which prevailed in every isolated nook 

 during the formation of the coal ; but examining the geological records 

 (the fossil life preserved in the rocks) we arrive at the conclusion that, 

 in these exceptional cases, the matter which afterwards formed the coal 

 accumulated in narrow, sheltered valleys adjacent to the sea, in places 

 where, after its gradual submersion, it was not subject to the action of 

 streams or rivers laden with sand or mud or other detritus. 



Again pursuing the order of events which followed the deposition 

 of the coal, we find that the blue clays and green sands were followed 

 by shelly and coralline sands, which now form the well-known Whano-a- 

 rei, Waipa, Raglan, Mokau, and Oamaru limestones. These are simply 

 local names for the same limestone, which is, perhaps, one of the most 

 marked, constant, and characteristic geological horizons in New Zealand, 

 and seems to form the natural close of the coal formation. Now, this 

 limestone is followed throughout New Zealand quite conformably by a 

 great series or succession of sands and clays, which in the classification 

 of the New Zealand Geological Survey possesses the generic name 

 "grey marls," or " Waitemata Series." These sands and clays are 

 typically developed on the shores of the "Waitemata, which has given its 

 name to the rocks of this period throughout New Zealand. The Waite- 

 matas, as seen at Fort Britomart or the Calliope Dock, consist of 

 rapidly alternating layers of clays and soft sandstones. The presence in 

 these of numerous broken plant remains, and sometimes thin, irregular 

 streaks of coaly matter, together with the almost entire absence of true 

 marine beds, clearly points to the prevalence of fluviatile conditions 

 during their deposition. 



