Hill. — Geology of Hawke's Bay. 475 



directly as the pressure; consequently the land and water con- 

 trasts at the present time are, on the average, comparatively 

 small. But those contrasts widen under the conditions de- 

 scribed in fig. 3, and they increase still more under the con- 

 ditions assumed to exist in fig. 2. Now, it seems to me that 

 either of the conditions illustrated in figs. 2 and 3 would be 

 sufficient to bring about results such as the flora and fauna of 

 the Pleistocene period show to have existed before, during, 

 and after what is said to have been the glacial era. A pres- 

 sure of 16- 161b. to the square inch under No. 2 condition, or 

 of 17151b. under No. 3 condition, would have produced strong 

 contrasts in the animal and vegetable world, for on the one 

 hand the temperature in the area approaching the sea-level 

 of the earth's surface must have been high, whilst in close 

 proximity the high lands w r ould undergo all the rapid changes 

 of temperature such as one meets with in the higher regions of 

 the atmosphere, where the air is so rare that it is unable to 

 hold much moisture, and, as a result, radiation takes place at 

 a very rapid rate. 



Here, then, I think we may look for light in explaining 

 the phenomena of the Glacial period, with its antecedent 

 and subsequent changes. In his " Fragments of Earth-lore," 

 page 270, Geikie says that " the Glacial, Pleistocene, and 

 Post-glacial periods are not sharply defined, but merge," and 

 he would like " one general term to include both. They form 

 together a tolerably well-defined cycle of time, characterized 

 by its remarkable climatic conditions, which were most 

 strongly contrasted in the earlier stages of the period. Also, 

 it appears that various oscillations of surface appear to have 

 taken place again and again in the earlier and later stages of 

 the cycle." The contrasts in temperature which must have 

 taken place on the earth's surface during the progress of the 

 physical changes such as I have shown to be possible without 

 the help of external causes would produce all those charac- 

 teristics which the glacialists say existed during the period 

 claimed by them as glacial ; but it further helps to explain 

 why traces of that period are not to be found over the entire 

 land-area known to geologists as the Pleistocene. The sur- 

 face of the earth does not undergo depression and elevation 

 synchronously. In one place areas may subside, in others 

 they may be elevated, and representing the same geological 

 period, and it may be that in one Pleistocene area the fossil 

 life — both the fauna and flora — may show wide climatic 

 variations, whilst in another there may be hardly a trace of 

 such. In any case there seems to be no need to seek for 

 external causes to bring about the cold period which marks 

 the fossil fauna and flora of the later Pleistocene times. 

 Earth-movements in combination with atmospheric pressure 



