Mackay. — On the Glacial Period. 447 



Art. LXX. — The Glacial Period of New Zealand, 

 By Thomas Mackay, C.E. 



\Read before the Nelson Association, 5th April, 1875.] 



To THOSE who in their wanderings throughout New Zealand look with a 

 geological eye at the many evidences they meet with of a glacial period, it is 

 obvious that the moraines and drift formations — ^many of which form our 

 minor watersheds — have been the result of the same action as that to which 

 similar physical features in tropical climates are due, namely, the breaking up 

 of vast bodies of long accumulated ice, with its stored up forces, in the high 

 altitudes of their great mountain systems. There was doubtless a period in 

 which the region of which this now insular country formed a part experienced 

 greater extremes of temperature, while at the same time the mountain ranges 

 were of a higher elevation than now. 



The time, however, of this, or of the changes of eccentricity in the earth's 

 orbit that occasioned the geological revolution, or whatever it may be termed, 

 which supervened, is still to be discovered. By the forces exerted in the 

 latter catastrophe the vast masses of rocks and diluvium were transported to 

 the sites of, and piled up into, the moraines and drifts we now see around us. 

 Assuming, therefore, the present hypothesis to be correct, if ever the periods of 

 alternation of cold and heat in geological times can be measured^ an approxi- 

 mate test of the time which has elapsed between geological epochs may be 

 determined, but to do this a reconcilement between cosmical time and 

 geological time must with some certainty first be established. Whenever such 

 a complex problem is solved, a basis of calculation may then be formed by 

 which to measure the distance of time at which our glacial periods happened. 

 For the present, palseontological research is the best key, and when the critical 

 tabulation of the large collections of New Zealand fossils has been completed 

 by Dr. Hector, it will afford a surer criterion than formerly by which to test 

 the several speculations that are current respecting the geological characteristics 

 of New Zealand, and to establish more correct theories regarding them, 

 particularly of recent formations. 



While geologists are not yet able to mark the point of union between 

 historical and geological time, nor competent to define when geological epochs 

 terminate and the historical era begins, still, by the aid of palseontological 

 researches and collections, comparisons can be instituted, and indirect inferences 

 formed of the mineral and physical relations of geology proper with the 

 conditions of existence which plants, animals, and the human race bore to 

 each other in prehistoric ages. 



