Correspondence — Mr. James Hector. 05 



And thoKo, wliotlior tlioro still exists a force to check the further 

 doscoiit of silt, or tli.-it this has Ixsou romovod, or ncoer exintcd there 

 at all, are, I venture to maintain, the result of the process I have 

 described. And of this even Mr. Mackintosh, I tliiuk, will convince 

 himself, if he will only cut through a few of theui, and fairly examine 

 their composition. 



Of course I must not be understood as denying that many banks 

 in valleys have been formed on either side of a running stream by 

 its erosion, whether during floods, or when the stream ran at a 

 higher level than at present. It is the " marine" origin of the 

 terraces in question, to be seen scoring the flanks of our Chalk and 

 Oolite liills, often up to their summits, which I have controverted. 

 And although Mr. Mackintosh has now withdrawn the phrase 

 " raised sea-beaches," as applicable to them, and substitutes those of 

 " raised coast-lines, tidal terraces, or current-marks" (p. 26 supra), 

 I do not think he thereby mends his position in any degree. 



G. POULETT-SCROPE. 



GLACIAL EPOCH IN NEW ZEALAND. 



Sir, — I observe that several writers who discuss the debatable 

 land between Geology and Physical Geography assume that in the 

 Southern Hemisphere signs are found of a Cold Period, analogous 

 to the Glacial Period of the North, and any difference of opinion on 

 the subject is only as to whether the extreme cold affected both 

 hemispheres at the same time, or alternately. I am aware that 

 descriptions of this Glacial Epoch, and the formations by which it 

 was supposed to be recognized in New Zealand, was given by Dr. 

 Haast, prior to 1864; but towards the close of that year he com- 

 pletely changed his views on this most vital point in New Zealand 

 Geology, and adopted the explanation of the former extension of the 

 Glaciers in the New Zealand Alps, which was first suggested by 

 myself in 1863. 



Those who are interested in this subject will find the more modern 

 view fully stated in the English translation of Hochstetter's work, 

 the essential points being given in my own words (Hochstetter's 

 New Zealand, 1867, p. 505). As the author does not give this 

 important passage as a quotation, reference may be made to the 

 Journal of the Eoyal Geographical Society, 1864, p. 103 ; while at 

 page 92 of the same volume of the Journal, the opposite hypothesis 

 of the submergence of the island and contemporaneous ice-cap 

 diiring a Glacial period, is clearly stated by Haast. 



This latter theory is quite irreconcilable with the observed facts, 

 and the former extension of the glacier is sufficiently accounted for 

 by the gradual reduction of the surface area exposed above the per- 

 petual snow-line : firstly, by its erosion into valleys, ridges, and 

 peaks ; and secondly, by its gradual subsidence — a subsidence which 

 has operated for the most part continuously — though interrupted by 

 irregular and local elevations. Some of these have occuri'ed since 

 the arrival of colonists, even to the extent of nine feet. But beyond 

 fifteen to twenty-five feet above the present sea level, no marine 



