50 
THE VOYAGE OF H.M.S. CHALLENGER. 
ir: i. as far as the Indian Isles, the Philippines, and China. (3) The Hyperborean 
< > >a: ( Oec'-mus Hype rborseus), the north ocean stretching around the Arctic 
in.''. (4) Ocean hs Australis surrounding the Austral continent, of which the Indian 
Ocean is only a part. Other geographers, adds Varcnius, divide the ocean into four 
parts, and adopt the following subdivisions: — (l) The Atlantic, to the north of the 
■■{U.itor; (2) the Aethiopian Ocean, to the south of the equator; (3) the Pacific Ocean; 
uid (4) the Indian Ocean. But he does not seem to attach great importance to this 
nomenclature; he says: — “Res non est magni momenti ; sequatur quilibet quod ipsi 
optimum videtur. Magis enim a nostra fictione quam a natura dependet hsec divisio.” 
It i.' important to note that this is the first time we find the Atlantic subdivided 
into two parts, as practised in our day. According to Kriimmel, Guillaume Delisle 
adopted the following designations: — (1) The North Sea for the whole of the Atlantic 
with the name generally written north of the equator, although in certain maps it 
ippcars south of the equator; (2) the Indian Ocean ; (3) the South Sea, occasionally 
calk- : the South Sea or Pacific, sometimes the Great South Sea, but these names 
always apply to the whole Pacific. 
l • ( The first attempt to represent the bottom of the sea by isobathic curves is to 
1m* found in a map by Philippe Buache in 1737. These isobathic curves are in- 
i' tu: d to show that certain elevations of the sea-bottom correspond with the orography 
-f the neighbouring land. In his Essay on Physical Geography, 1 published in 1752, 
he. develops these ideas, which may be summarised as follows : — 
Aft* ;• the dtluge the summits of the highest mountains formed a small number of 
i 'lands ; the waters falling, other islands of less altitude soon appeared, but still separated 
ft'' <m lie first. The waters continuing to recede, the higher ridges uniting these islands 
g m to show themselves, then the table-lands formed by masses of mountains became 
vis’ble, and finally the lower plains appeared. Had the water still continued to 
iv cede other lands would have appeared in succession, and the bottom of the sea 
would !••• a vast valley; it might then have been seen how the basins of the 
-* * are diversified, and how the continents are united by submarine chains now 
li i i< ii from view by the waters covering them. The directions of certain chains 
of i-land', of rocks, of shallows, which cross the sea, seem to unite the chains of 
’ 1 rr* - ml mountains. The soundings of navigators, the observations on the currents 
and their directions, arc almost incontestible proofs that the bottom of the sea differs 
from tli<* land only in that it happens to be below the line at which the waters 
ceased to recede. 
I... f.< K.<*a i ;• .;raphie physique, oil 1’on piopose des vues gendrales aur l’espcce de cliarpente du globe, 
: ‘ rn-.nu *n<-« qui traverent lea men cornnie lea terres ; avec quelques considerations particulifcrcs 
r 1 rrnU ba**;n« de 1* tner et ear n configuration intdrieure (Hist, de C Acad . des Sciences, 1752, pp. 39!) 
