BY E. C. ANDREWS. 179 



The appearance of the coasfcal area is explained by the forces 

 of subaerial denudation acting on a plateau till a period of 

 maturity and old age, when the general outline of the upland 

 would have vanished, with only a few mountains left amidst the 

 undulating country to show its former extent. The extreme old 

 age of this area will be reached when it is reduced to a peneplain. 

 It must be remembered that mature dissection of an upland is 

 not necessarily associated with a mature neighbouring coast, since 

 the ranges may have been developed to this stage in a cycle pre- 

 ceding a crustal movement which would place the coast line in its 

 initial stages when the other was alread}'- mature. 



The frequent occurrence of wide and very thick masses of river 

 gravel underlying the various Tertiary basaltic flows of the table- 

 land, and now associated with the present insignificant strearas 

 only, points to a cycle of erosion antedating the present one. 

 In this first cycle several basaltic outbursts occurred, and 

 the present 3,000 feet level of the New England plateau was 

 developed near sea-level, since which period a 3,000 feet eleva- 

 tion has taken place and the present coastal forms evolved. The 

 upland elevation and coastal subsidence"* indicate a differential 

 movement from east to west, while the various phases of shore 

 development show a variable movement from north to south. 

 The subsidence was accentuated seawards, therefore the Barrier 

 Reef is probably of some considerable thickness, though forming 

 but a mere fraction of the mass of the continental shelf. 



One of the most instructive and interesting features in connec- 

 tion with this subject is the still more recent differential movement 

 from east to west. On the most easterly limit of the Great 

 Barrier no records exist of any trace of elevatory movement; 

 closer in shore Mr. Jukes and Professor Agassiz found abundant 

 signs of a slight movement varying from 5 to 20 feet above 

 H. W.M. Large terraces and coastal plains exist on the mainland, 

 up to as much as 300 feet in one instance. 



On the eastern uplands themselves the recent streams which 

 ha^•e flowed over the plateau in broad and shallow basins now 



* The coastal subsidence, however, postdated by a long period of time the 

 last considerable elevation of the plateau. 



