OCEAN CONTOURS, S.W. PACIFIC. ^33 



Appeal lias frecjuently been made to ocean soundings and to the 

 contours that they reveal, but in such cases the material on which the 

 appeal has been based is chietly the map published in the " Chal- 

 lenger" records, which has been copied with but slight alterations into 

 many other publications. In general but little attention has been 

 paid to the geological matters so far as structure and composition of 

 the various land masses are concerned. 



In this paper an attempt is made to embody the most recently 

 recorded soundings that could be obtained in a general bathymetric 

 map in order to show the most probable land connections that may 

 have existed in the past, on the assumption of the general elevation 

 of the whole region. Of late years many important memoirs on the 

 geology of the islands in this area have been published. An attempt 

 is here made to bring together the results of these memoirs, and to 

 consider them with regard to the structure of Australia and New 

 Zealand. 



Ocean Contours. 



The soundings recorded in the British Admiralty charts are 

 rather numerous in the area between New Zealand, Samoa, New 

 Caledonia, and Australia, and it is possible to arrive at what is 

 probably an accurate idea of the nature of the ocean floor within these 

 limits. Eastward the soundings are relatively few, but this is the 

 less regrettable because those that are recorded suggest that the ocean 

 floor is relatively flat all over the western part of that portion of the 

 Pacific Ocean lying east of New Zealand, and that it lies between 

 2,500 and 3,000 fathoms from the surface of the water. 



Southward, fi'om New Zealand, shallow water appears to extend 

 some distance, and the great depths of the area previously mentioned 

 are nowhere attained, though, between the New Zealand Plateau and 

 South Victoria Land, intermediate depths of 1,500-2,000 fathoms 

 probably extend over a wide area, and the water appears to shallow 

 gradually as the southern land is approached. 



Westward between New Zealand and Australia the Tasman Sea 

 is as far as known uniformly over 2,000 fathoms in depth, and its 

 basin slopes steeply from the Australian Coast and from the south- 

 west coast of New Zealand, though further north on this eastern side 

 the steep slope recedes from the New Zealand Coast. 



These general facts are recoi'ded in many works of reference, and 

 the main features are to be seen in maps printed in text books, such 

 as '■ Chamberlain and Salisbury's Geology,'' " Berghau's Physical 

 Atlas," and many others. In nearly every case these are based on the 

 map printed m the '" Challenger" reports, A"ol. XXXVII. 



They all have the objection that Mercator's projection is used, 

 and this, of course, gives an overwhelmingly disproportionate area to 

 districts situated in higher latitudes. In most cases too little notice 

 is taken of the numerous soundings that have been recorded since the 

 date of the " Challenger" expedition. 



For these reasons a new map has been prepared for the purposes 

 of this paper. A projection has been employed which reduces the 

 disproportion referred to as much as practicable, and all the sound- 

 ings recorded in the most recent Admiralty charts have been incor- 

 porated, as well as a few obtained from other sources. 



2c 



