412 Transactions. — Geology. 



railway station also showed that the silt was stratified, but this section is 

 now obliterated by weathering, and I have thought it important to call the 

 attention of geologists to the section behind the dock while it is still fresh ; 

 for no doubt it will soon become obliterated like the one behind the railway 

 station. 



The origin of this silt deposit is of considerable interest, as it is im- 

 portant evidence in discussing the question of the latest oscillations of level 

 in New Zealand. Dr. von Haast, in his Eeport on the Geology of Canter- 

 bury and Westland (1879), p. 367, calls it " The Loess Formation," com- 

 pares it with the loess deposits of China described by Baron von Kichthofen, 

 and says that " the general character and position of the principal loess (or 

 loam) beds in this province prove clearly that they have been formed by the 

 modus operandi pointed out by Von Kichthofen." There is, however, one 

 difference which he mentions, " and that is the absence in the Canterbury 

 beds of the peculiar small marly nodules so common on the Ehine, the 

 Danube, and in China." 



The modus operandi in question is the following : The fine particles of 

 earth carried down the slopes by the rain are partly retained by the grass 

 growing on the slopes, and the dust blown across the land by the wind is 

 also retained by the grass, the roots of which also decay and assist in raising 

 the ground ; — so that the formation is a mass of grass covered with fine 

 earth and sand brought by the wind and the rain, and has, of course, an 

 entirely subaerial origin. It is characterized by being unstratified, and by 

 having a "peculiar vertical capillary texture," caused by the decay of the 

 roots of the grass. 



I am afraid that the well-marked stratification of the base of the Lyttel- 

 ton silt deposit can hardly be reconciled with this method of formation, 

 and there are several other difficulties which cannot, I think, be explained 

 on the theory of a sub-aerial origin. 



In the first place the deposit is widely distributed and rests upon beds 

 of very different mineral composition. According to Dr. von Haast it is 

 found at the foot of Mount Grey and on the Moeraki Downs, where it lies 

 upon tertiary argillaceous and calcareous sandstones ; at the Malvern Hills, 

 where it rests upon secondary sandstones and slates. At the southern end 

 of the Canterbury Plains it occurs from the Orari to Timaru, where it is 

 found on tertiary sedimentary and volcanic rocks ; and in some places it 

 lies on the shingle of the Canterbury Plains. South of Timaru it can be 

 traced beyond the Waihao, and in the valley of the Waitaki south of 

 Elephant Hill. From my own observations I know that it is largely 

 developed at Oamaru, where the base is also stratified, and that it extends 

 as far south as Moeraki Peninsula. It is difficult to understand how so 



