OlKKRAl'IIV AND 
Bathymetry nr 
mr Ara ip* 
Cora i. Isiaxiw. 
A BAR VlRVo 
kHAKMXO THE 
Amo* or Water. 
34 THE VOYAGE OF H.M.S. CHALLENGER. 
v ■ 1> two principal branches into the land masses. The eastern branch forms the China 
N'.i, tie Indian Sea. t lie Arabian and Persian Gulfs, and the Sea of Zanzibar: the 
u. t rn 1 ranch forms the Mediterranean. The water of these branches is derived from 
tl ii ■ iiu o -i an. Navigation is confined to the branches, no ship having traversed 
tlx cm-ircling sea. Yacut states that the inhabited climes are all north of the equator. 1 
The Vrabs have left very few documents relating to orography or bathymetry. It 
i.- i ir- ly that we find in their writings even an evaluation of the heights of mountains. 
Ibn Khaldun, who, in the fourteenth century, wrote his celebrated History of the Berbers, 
n m rks that if the highest mountains are situated near the sea, it must be regarded as 
a providential arrangement to arrest the invasion of the ocean. 2 The Arabs do not seem 
t.. iv liven aware of the significance of volcanic phenomena from a geological point 
■f view. They admitted, however, that the surface of the globe was subject to changes ; 
ha: tlx ' might occupy the place of the land or be confined within narrower limits. 
We find them recording observations on the formation and destruction of coral 
1>. Vl-Biriini 3 points out that in the Laccadives and Maldives several islands 
ink bt neath the waters, while others were raised above them, so that they became 
1: ibitabh one after the other. He says : — “The name of Dyvah is given to islands that 
t * r i *_r i n.it e in the sen, and appear above the water in the form of sand-banks; these banks 
ii growing extend and unite till they present a solid aspect. At the same time others 
• >f these islands by breaking up decompose, melt, and disappear in the sea; when the 
inhabitants perceive this, they retire to some new island that is on the increase, transport 
int i these th.-ir cocoa-nuts, palms, grains, and utensils, and finally establish a new home.” 4 
N lions concerning the geological action of water, and the sediments carried into the 
i and then solidified, are met with in the writings of Kazwini. 6 Al-Bimm, whom we 
!n\. ju t cit' d, embraced the idea previously expressed by Megasthenes, 6 according to 
wh i Bengal has been formed by the accumulation of sediment deposited by the Ganges. 
A Min imi al s* . shows that he had observed the distribution of materials transported by 
v iter. II point- out that the larger fragments are laid down at the upper parts of 
riv that grav i ! is formed in the lower portions of their course, and that, finally, sand 
and the finer particles are carried into the ocean. 7 
W find in M Mud! examples of the carriage of fluviatile sediments, the accumulation 
f Mibb causes the ■ a to retire. He had been profoundly impressed by the sanding-up 
1 Yacut, Diet., Leipzig, 1866, pp. 601, 604. 
* I u K’ i in, Hiitoiri .Ii Berbers, trad, de 1’Arabe par M. Slane, Paris, 1852, tom. i. p. 194. 
* Flourished about 1000 a.d. 
* . - • 1 1 ■ ii i, by s.v:hii i, London, 1888, p. 106, and Al-Blrunl, Reinaud, No. III., “Extrait de l’Ouvrage 
'Altar 'ini *ar l'Inde, Journal Anatique, ser. 8, tom. iv. p. 265, 1884. 
‘ K : ni' r ij : . , n/icb der Wustenfiddiohen Textuuegabe, aus dem Arabisclien von H. Ethe, Leipzig, 1809. 
M* „ i- h v i- • nt t India by Set acus about 3'»2 B.C., and was probably the first Greek to reach the banks 
( ; • > i rig> «, . r; nlv 1 1.*- tut * riter to gi\e an account of the country from personal observation. 
1 AlWroni'a India, Sacbau, p. 198. 
