TRANSACTIONS OF SECTION E. 703 



over, ■wliich the general level of the water rises, while the northerly wind continues 

 to blow throughout the northern half. 



At either of these times I think it is highly probable that there is an under- 

 current in the opposite direction to that at the surface, but unfortunately the sea 

 disturbance is great and observations are very difficult. 



Observations were, however, made by Captain W. U. Moore in II.M.S. 

 ' Penguin ' in 1890, but at a time when the change of monsoon was tailing place. 



The result was peculiar, for it appeared that at a depth of about 360 feet 

 the movement of the water was tidal, while the surface water was moving slowly 

 in one direction — a result generally similar to that obtained by the Americans in 

 the West Indies— but the direction of the tidal flow was directly opposite to what 

 might have been expected, viz., the water ran in while the tide fell, and vine versa. 



More observations are, however, needed here before any certain conclusions can 

 be formed. 



The depth of the ocean is the next great feature which demands attention. 



On this our knowledge is steadily, though slowly, increasing. 



The whole of it has been gained during the last tifty years. 



Commenced by Sir James Ross, whose means were very small, but who never- 

 theless demonstrated that the so-called unfathomable ocean was certainly fathomable 

 everywhere, the sounding of the ocean has continuously proceeded. The needs of 

 submarine cables have constantly demanded knowledge in this particular, and the 

 different cable companies have had a large share in ascertaining the facts. 



Expeditions, whose main object has been to obtain soundings, have been sent 

 out. Great Britain and the United States taking the first place ; but moat maritime 

 nations have aided. 



In the immediate past the additions have mainly been from the soundings 

 which H.M. surveying ships continually take whenever on passage from one 

 place to another, from the work of our cable companies, and from United States 

 vessels. 



We have, as a result, a very fair general knowledge of the prevailing depths in 

 the Atlantic, but of the Indian and Pacific Oceans it is very fragmentary. We 

 have enough to give us a general idea, but our requirements increase as years 

 roll on. It is a vast task, and, it may be safely said, will never be completed ; for 

 we shall never be satisfied until we know the variations of level under the water 

 as well as we know those on the dry land. 



It is hopeless to do more than to briefly sketch the amount of our knowledge. 



First, as to the greatest depths known. It is very remarkable, and from a 

 geological point of view significant, that the very deepest parts of the ocean are 

 not in or near their centres, but in all cases are very near land. 



One hundred and ten miles outside the Kurile Islands, which stretch from the 

 northern point of Japan to the north-east, the deepest sounding has been obtained 

 of 4,655 fathoms, or 27,930 feet. This appears to be in a deep depression, which 

 runs parallel to the Kurile Islands and Japan ; but its extent is unknown, and 

 may be very large. 



Seventy miles north of Porto Rico, in the West Indies, is the next deepest cast 

 known, viz., 4,561 fathoms, or 27,366 feet ; not far inferior to the Pacific depth, but 

 here the deep area must be comparatively small, as shallower soundiajs have 

 been made at distances sixty miles north and east of it. 



A similar depression has been sounded durinar the last few years west of the 

 great range of the Andes, at a distance of fifty miles from the coast of Peru, where 

 the greatest depth is 4,175 fathoms. 



Other isolated depths of over 4,000 fathoms have been sounded iu the Pacific. 

 One between the Tonga or Friendly Islands of 4,500 fathoms, one of 4,478 fathoms 

 near the Ladrones, and another of 4,428 fathoms npar Pylstaart Island, all in the 

 W'e.'itern Pacific. They all require further investigation to determine their extent. 



With these few exceptions, the depth of the oceans, so far as yet known, nowhere 

 comes up to 4,000 fathoms, or four sea miles; but there can "be little doubt that 

 other similar hollows are yet to be found. 



The sea with the greatest mean depth appears to be the vast Pacific, which 



