1916.] THE DEPOSITS. 367 



with other types showing climatic changes and changes of 

 elevation. 



It must be noted that the type here described, being the 

 result of the aerial weathering of a saturated and partly 

 decomposed rock, consists of angular pieces of rock, partly 

 softened on their exterior surfaces mixed with the sand and 

 clay which has been derived from the completely decomposed 

 portions, hence the resulting rubble is a mixed mass of loose 

 angular stones with clay and gravel. This type cannot easily 

 be mistaken for any other kind. 



2nd.-HEAD PRODUCED BY FROST. 



This type is quite distinct. It consists of angular stones 

 of all sizes which may be (on the flat) in situ or may have 

 been moved short distances by various agencies. Where 

 these stones have been separated from a cliff they have fallen 

 to the base, and if not subjected to erosion have maintained 

 their angular surfaces, but it must be noted that theses-angular 

 surfaces are parallel to the jointing because the frost that has 

 separated them from the rock masses has acted by freezing 

 the water in the joints. This type is, therefore, an indication 

 of an elevated land and severe climate. 



3rd.-DEP0SITED HEAD. 



This consists of clays, gravels and easily moveable 

 material which has been redistributed, and may be a mixture 

 of all other kinds of " Head." These deposits must be 

 determined by their separate and distinctive characters. 



STREAM GRAVELS. 



Under this heading I class any deposits which may have 

 been washed down from high to low levels consisting of 

 disintegrated rock material, rolled or unrolled, by rushes of 

 water or by rain sufficiently heavy to cause the deposit to 

 remain unmixed with surface detritus. 



The " Head '' in Guernsey consists of all the described 

 kinds, and covers the whole period of time since the Pleisto- 

 cene deposits were begun. 



In the chapter on " Emergence " I have described the 

 earliest deposit and in the proper places I shall describe the 

 other subsequent deposits, but to have their order in mind 1 

 shall enumerate them here. 



1st. — Blocks and stones of all sizes detached by frost 

 acting in the jointing of the rock. Such stones are angular 

 and retain their natural faces. These belong to Class 2, 

 (See above.) 



