340 " ENDEAVOUR " SCIENTIFIC RESULTS. 



From 60 to 100 fathoms, apart from being narrow and rocky, 

 the shelf is frequently so steep as to form part of the general 

 slope downwards to abyssal depths. 



Southwards from Smoky Cape the relative proportion 

 between the inner and the outer areas become reversed. At 

 the Cape itself the shelf is narrow and divides into two equal 

 belts ; the shallow area of less than 50 fathoms and a deeper 

 stratum with an average depth of 70 fathoms. From here 

 southwards this outer stratum l)ecomes gradually wider at 

 the expense of the inshore or secondary ledge and a maximum 

 width of which is found in the Newcastle Bight, where the 

 inshore ledge is seven to eight miles wide, while the outer 

 extends for another twenty-one miles before breaking off 

 into the deep. Simultaneous \A'ith the appearance of the 

 outside ledge at Smoky Cape the depth of the " break off " 

 increases quickly to about 100 fathoms and remains so for 

 the remainder of the coast south to Gabo Island. 



An interesting, and, as will be shown, very important 

 feature of the outside ledee is the nature of the bottom, which 

 in most parts, consists of fine sand mixed with mud. Kocks 

 are very rarely met with and are practically confined to the 

 outer margin ; but the inshore narrow strip of less than 50 

 fathoms is in most parts rough and so also is the area between 

 the two ledces where in some parts there appears an almost 

 vertical rocky wall fully one hundred and twenty feet high 

 and running parallel to the coast. 



These conditions continue southwards for nearly four 

 hundred miles to near Twofold Bay, the only interruption 

 being opposite projecting headlands, where the influence of 

 confined currents prevent the accumulation of deposits and 

 leave the " foundation " — the rocks and boulders — practi- 

 cally bare. The nature of the shelf near Twofold Bay and 

 southwards to Gabo Island differs in a mai'ked degree from 

 the conditions just described, for here the " slope " is even 

 and continuous seawards to approximately lOri fathoms, and 

 while the area inside the 50 fathoms is perfectly smooth and 

 covered with sand and mud, the outer portion is rough and 

 near the edge has the semblance of a stone quarry. On one 

 occasion when for the purpose of some investigations the 

 '■ Endeavour " was anchored eleven miles to the east from 

 Green Cape considerable difficulty was experienced in recover- 

 ing the kedge anchor used ; the wire cable employed was 

 caught under several ledges in such a manner that it became 

 necessary to steam in a circle to free it, and the anchor, when 

 recovered, was twisted almost beyond recognition. 



