12 president's address. 



Sailing out of Sydney with the "Erebus" and "Terror," in 

 August, 1841, Sir James C. Ross was surprised to find the tem- 

 perature of the surface of the sea rise from 55° in the liarbour to 

 63° immediately outside the Heads. From subsequent observa- 

 tions he concluded that the breadth of the warm current running 

 to the southward at the rate of about twenty miles a day along 

 the coast of New South Wales does not much exceed three 

 hundred miles.* 



We still owe the best description of the Notonectian to the 

 "Challenger" Expedition. In June, 1874, the survey directed 

 by Sir George Nares found the current in reduced circumstances. 

 After a continuance of westerly winds, it was developed as a 

 stream thirty miles broad running at an average rate of one and 

 a half miles an hour, its inner edge twenty miles from the land. 

 The temperature stood at 69° to 70'7°, whereas the ocean 

 traversed by the current was only 63°. In the previous April 

 the same expedition found the current in a more vigorous con- 

 dition running close in shoi'e with a higher temperature of 72*^.1 



In an interesting study of local atmospheric conditions, Mr. H. 

 C. Dannevig has discussed this current in relation to the dispersal 

 of fish ova. From data collected by steamers running between 

 Sydney and New Zealand, he considered that the centre of the 

 warm current lies normally from a hundred to a hundred and 

 fifty miles east of Sydney. During stormy l)lows from the west, 

 the current is pushed bodily seawards, but in easterly weather 

 its western border brushes along the headlands. J 



[2) The Continental Shelf. 



The continental shelf may be defined as tliat area extending 

 outwards from the land to a depth of about one hundred fathoms. 

 This distinction is not arbitrary, for at or about this point the 

 sediment alters to finer and the slope of the sea-floor to steeper. 



* Ross, Voy. Discovery Antarctic Regions, ii., 1847, p. 5. 



t Chall, Report, Narrative, i., 188.5, p. 464. 



+ Dannevig, Journ. Roy. Soc. N. S. Wales, xli., 1907, p.4;i 



