SUPERFICIAL DEPOSITS. 



numbers. The remains of rodents, of ruminants, also of large 

 pachyderms and of birds, which have been dragged as prey to 

 \hese resorts, are also found. 



SUPERFICIAL DEPOSITS. 



" The regularly stratified deposits, of whatever geological period they 

 may be, are in most parts of the world covered up, more or less, by a con- 

 Biderable mass of heterogeneous material derived from the degradation of 

 the more anent rocks. This mass is generally unstratified, and deposited 

 in irregular heaps, partially filling up valleys, covering low tracts of level 

 country, and sometimes even capping low hills, but almost always bearing 

 marks of having been transported from a distance over ranges of high 

 land, although not without some reference to the present physical features 

 of the country over which it has travelled. 



"Occasionally the fragments which have been thus conveyed are of large 

 size and angular, and in this case they are called "boulders," or "erratic 

 blocks ;" but such masses have not generally travelled to any very con- 

 siderable distance from the parent rock. The transported fragments are 

 much more commonly of small size, and rounded, as if by mutual attrition, 

 at the bottom of the sea ; and in this state they have been often carried to 

 very great distances, and are found many hundred miles from the place 

 whence they seem to have been derived. They are then called ' gravel,' 

 and are not unfrequently mingled with bones and fragments of bones of 

 large quadrupeds." Ansted. 



32. These superficial deposits are termed DRIFT, and comprise 

 deposits of water-worn, transported materials, consisting of gravel, 

 boulders, sand, clay, &c. 



33. Drift is divided into DILU'VIUM, or ancient drift, and ALLU'- 

 VIUM (from the Latin, alluo, I wash upon), or modern drift. 



34. The DILU'VIUM 

 (formed from the Latin, 

 diluo, I wash away) co- 

 vers up the tertiary depo- 

 sits, and contains fossils 

 whose origin dates back 

 to a period not very long 

 antecedent to the present. 

 In fact the dilu'vium, to 

 a certain extent, unites 

 the tertiary with the re- 

 cent period. It contains 

 the bones of large mam 

 mals, both of extinct and 

 recent genera and spe- 

 cies. Among them we 

 may perhaps place the 

 enormous megathe'rium 

 Fig. 178. Skeleton of the Megathe'rium. (fg. 178 from thfc 



32. What is meant by drift ? 



33. How is drift divided ? What is the difference between dilu'vium and 

 ullu vium ? 



