Scientific Intelligence. — Hydrography. 37 I 



hue is a general indication of soundings, and indigo blue of profound 

 depth. — -{Rear- Admiral W.H. Smyth, K.S.F., on the Mediterranean 

 Sea, p. 125.) 



6. Admiral Smyth on the Temperature of the Ocean. — The result 

 of my experiments leads to the conclusion that there actually exists a 

 very sensible diminution between the surface temperature and that 

 obtained at great depths, and the difference may be roundly esti- 

 mated at about one degree for every twenty fathoms of line near 

 the surface, save where the agency of subterranean currents may 

 be at work, for such streams are undoubtedly connected with oceanic 

 influences; but below about 180 fathoms, to our utmost depths, the 

 temperature varied but little from 42° or 43° of the Fahrenheit 

 scale. We found that at equal depths the warmth is rather higher 

 along shore than in the offing ; still no reliance can be placed here 

 upon thermornetrical indications of an approach to land or a great 

 bank, as taught in the Atlantic Ocean, and the supposed heating of 

 the waves is a mistaken sensation produced by the cooling of the 

 atmosphere in the meantime. The mere surface temperature is 

 very variable, according to the weather and the altitude of the 

 sun, differing at sunrise and in the afternoon by three or four 

 degrees, and even more. — (Rear-Admiral W. H. Smyth, K.S.F., on 

 the Mediterranean Sea, p. 124.) 



7. Captain Allen s proposal of converting the Dead Sea into a 

 north-eastern extension of the Mediterranean. — There is certainly 

 no natural feature of the earth's surface more astounding, or more 

 difficult of explanation, than the existence of this long deep fissure, 

 which, being 630 feet below the Mediterranean at the Lake of 

 Tiberias, deepens in the Dead Sea to 1300 feet below the general 

 sea-ievel. With the nature of the hilly country between the Medi- 

 terranean and the Sea of Tiberias we are pretty well acquainted, 

 and we are reminded by Captain Allen that a line of communica- 

 tion might be established without traversing any very high ground. 

 Hence it is possible that the modern spirit of enterprise might 

 adopt the suggestion of a ship canal, as shadowed out by this officer, 

 through which the waters of the Mediterranean, rushing for a number 

 of years, might be cascaded into the low country, and thus sub- 

 merging a great area, now pestilential and of little or no value, 

 render the Dead Sea a south-eastern extension of the Mediterranean. 

 But still there would remain a space of land to be cut through from 

 the Dead Sea depression into the Red Sea ; and the first question 

 is, what is the nature of that barrier, and what its altitude. 



But before we can arrive at any explanation of this problem 

 in ancient or geological geography, or form any rational con- 

 jecture of the eventual possibility of opening such a water 

 communication between Europe and Southern Asia, it is essen- 

 tial that the true physical features of the region, particularly 

 of the tract between the Dead Sea and the Red Sea, be de- 



