210 MR. JUKES-liRO'S\^i: AND PROF. IIARRISOX 



of the Christchurch llidgo. It is known us Golden Ilidge, and has 

 ;in elevation of from 700 to 877 feet ; the only ground of equal 

 height lies to the north of it, but is divided from it by a broad 

 valley which is nowhere much above 700 feet. 



The rise from one terrace to another varies greatly in vertical 

 height, being sometimes onlj^ a sloping bank or 10 feet high, 

 sometimes a very steep slope for 50 or ].00 feet, and at others a 

 line of cliffs. There are in fact minor and major terraces, the 

 former being only traceable for a certain distance, though this 

 is often several miles, while the latter form bold features that are 

 continuous through the coral area. 



The southern ridge has six well-marked terraces, the lower steps 

 being very conspicuous from the sea on the southern side. Six 

 terraces at nearly corresponding heights can be traced along the 

 eastern part of the island north of Bridgetown, the last ending in a 

 slope which rises rapidly from 400 to 500 feet, and is one of the 

 most marked features in the island. Above this there are at least 

 five terraces, the highest being between 900 and 1000 feet, and there 

 are other intermediate steps which are not so continuously traceable. 

 The surface of the terraces is seldom level, but undulates, and 

 often slopes gently outward towards the sea ; they are also traversed 

 by dry valleys or gullies which radiate from the central heights of 

 the island, and terminate either near the coast or in the broad 

 central valley along which the railway is carried. 



Where the step or rise from one terrace to another passes into ai 

 line of cliffs there are sometimes caves which appear to have been 

 excavated by wave-action. The old shore-lines in fact reproduce 

 the variations in the present shore-line of the island, which is in 

 some places only a sloping beach of coral-fragments banked against 

 a raised reef, and in other places is a line of cliffs from 20 to 60 

 feet high, exhibiting all the usual phenomena that are due to marine- 

 erosion. 



The parallelism of the lowest terraces to the present coast-line- 

 has been mentioned, but it is not entirely confined to them, for the 

 older and higher reefs up to at least 600 feet have the same 

 parallel trend, except of course where they are deflected into the- 

 transverse valleys ; and it is noticeable that where the modern 

 coast presents a line of cliffs the terraces behind them rise from 

 similar cliff-lines or from very steep slopes. These facts seem ta 

 show that but little, if any, alteration has taken place in the direc- 

 tion of the marine currents or of the prevalent winds since the 

 time when the formation of the higher terraces began. 



(b) Tliichness. — From the manner in w^hich these successive 

 platforms have been constructed, it follows that the thickness of 

 the coral-rock of which they consist must vary greatly in different 

 places, and this we find to be the case. The greatest thickness 

 will generally be found near the outer margin of each raised reef, 

 and its least thickness will be at the foot of the succeeding slope ; 

 but there are many exce]itions to this rule, in consequence of the 

 uneven surface on which the reefs have been built. 



