ICE MARKS. 221 



from terminal moraines by their position. Lateral moraines are more 

 likely to be imitated by landslips. 



Till Deposits. — There are three types of till, but they are often 

 mixed. (1) Sub-glacial till, or Boulder clay. A compact, tough clay 

 •with unassorted sand, gravel, and numerous boulders : the fragments 

 not much weathered but rounded, often scratched and sometimes 

 facetted. The fragments are mostly derived irorn the immediate 

 neighbourhood, but partly from a distance, sometimes up to several 

 hundreds of miles, This is a ground moraine, and the subjacent rock 

 is alw T ays planed, polished, and striated or grooved. (2) Surface till, 

 or moraine till. This lies on the first and is more sandy and looser 

 but unassorted. The rock fragments are larger, more angular, rarely 

 scratched, and more decomposed than those of the Boulder clay. 

 This till is probably surface moraine of the ice-sheet which has been 

 left when the ice melted. (3) Floe till, or berg till. This is composed 

 of more or less assorted sand, and clay indistinctly laminated and 

 containing erratics often scratched. It is either marine or else has 

 been formed in lakes round the end of the ice. Large boulders are 

 sometimes rare. Counterfeits of till are not common. Nevertheless 

 in regions of severe and sudden storms boulders four feet or more in 

 diameter are known to have been transported by the rush of water 

 and left in the midst of mud and fine sand. During the flood in the 

 Waimakariri on the 18th March, 1888, at Kaiapoi, several 30-ton 

 blocks of concrete were carried for nearly a quarter of a mile and 

 buried in sand. 



Karnes. These are narrow ridges, 20 to 50 feet high, formed of 

 rounded gravel and sand discordantly stratified, the stratification 

 often conforming to the surface, thus proving that they are not due 

 to denudation. They commonly contain large boulders. Sometimes 

 two run together and form a valley without an outlet. Generally 

 they pass into terraces. They are found at the mouths of valleys and 

 are more or less transverse to it. They are also always associated 

 with moraines. They are, no doubt, due to violent currents of water 

 operating near the front of a glacier and are probably the fans of 

 glacier rivers. 



Otars, or Serpent Karnes are longitudinal to the valley, and the 

 materials composing them have come from greater distances than 

 those of the neighbouring till. No doubt they have been formed by 

 glacial, perhaps sub-glacial streams. 



Drumlins are elliptical hills with steep sides and rounded tops 

 formed of morainic matter, the long axis always in the direction of 

 movement of the former glacier. Probably due to ice riding over old 

 moraines. 



Perched Blocks, often in precarious positions on the tops or sides 

 of hills or mounds, are very characteristic of ice action. They may 

 occasionally, but not often, be counterfeited by blocks brought down 

 by landslips. 



Erratics. May be merely blocks, larger than water could move, 

 brought down a valley. Or they may be blocks which have been 

 lifted up above their place of origin. Or they may be blocks which 



