TILE VOYAGE OF H.M.S. CHALLENGER. 
PoLTBJUa 
Crate* • >v 
Maijat*. 
*J0 
ind water; each new point on the globe, when correctly determined, could be placed on 
t' tp with great exactness. At this time the science of oceanography may be said 
h v Veil founded. The navigator could henceforth direct his vessel into unknown 
seas, could return by the same or another route, and could point out to others the course 
he had followed. (Sec Plate III.). 
Hipparchus regarded the whole habitable world as divided into eleven climates or 
zones of latitude, for each of which he indicated the length of the longest day. He had 
als<> a dim idea of connecting distant points by a kind of triangulation similar to that 
made use of by modern geographers. He did not admit that the Atlantic and Indian 
0 :eai were connected towards the south of Africa, or that the former was united with 
th» sea that bathes the northern shores of Scythia. 1 These views were apparently 
based on some observations of a Babylonian author, named Seleucus, with reference to 
t t h , which appeared to Hipparchus incompatible with the idea of a circumfluent 
and continuous ocean. 
The historian Polybius, 2 a contemporary of Hipparchus, in like manner, did not 
admit it as proved that the habitable world was surrounded by the ocean. 3 This 
.■utl: >r had more advanced ideas regarding marine sedimentation than his predecessors; 
h points out that in the Palus Maeotis the rivers bring down considerable quantities 
of sediment, and estimates the time it would take for the fluviatile alluvium, not 
only t - fill up the Palus Maeotis, but also the Pontus Euxinus or Black Sea, 4 The 
ideas of Polybius, from a geological point of view, are most reasonable, but the rate of 
encroachment has been much slower than he supposed during the two thousand years 
wl i separate us from the time when he wrote. The modification in these seas has 
no 1 been very appreciable, for Polybius reports that in his time the greater part of the 
S > ■ f Azov was only from 5 to 7 fathoms deep, and the same depths are marked on 
modern hydrographic charts. 
Polybius also gives a detailed evaluation of the dimensions of the Mediterranean. Its 
1* : _ T ih from the Strait of Gibraltar to Selcucia in Syria he gives at about 2440 miles, or 
10,52" stadia, — a calculation nearer the truth than that of Eratosthenes, and short of the 
r d length by only 5 00 stadia — and to it he assigned a width of 3000 stadia. This was 
■ o:,-'derably less than the reality, and caused him to bring the coasts of Gaul and 
1 _ : much too fa” towards the south. 5 Polybius had probably received some dim, 
t: • . 1 1 i 1 1 g tradition of the populous and fertile regions south of the Soudan, for lie states 
tlii* the immediate neighbourhood of the equator is much less hot than the torrid zones 
on either -idc, and that it was habitable — indeed, inhabited. 
A: "Ut this tine Crates of Mallus® is said to have constructed the first globe on which 
b. Atlantic Ocean i- extended t*> the south pole. A corresponding ocean is placed on 
1 Strnljo, i. 1, 9. 
* Polrbiu*, iv. 39-4?. 
* 204 to 122 B.C. 
* See Bunbury, op. rii., vol. ii. p. 35. 
3 Polybius, iii. 38. 
9 Flourished about 150 n.c. 
