186 ANNIVEESAEY ADDRESS 



equally diversified in the one case by oceanic currents on the 

 surface as well as on the bottom, and in the other by foaming rivers 

 and gentle streams. I will give a few instances of such inequalities 

 in the North Atlantic. In 1878, while repairing the Anglo- 

 American cable, a tract of rocky ground, about 100 miles in length, 

 was discovered, in the middle of the JS^orth Atlantic, between 

 33° 50' and 36° 30' West longitude, and about 51° 20' North 

 latitude. "Within a distance of eight miles the shallowest sounding 

 was 1370 and the deepest 2230 fathoms, a difference of 860 fathoms 

 or 5160 feet; within four miles the difference was 3180 feet, and 

 within half a mile 1380 feet. There are also the Laura Ethel 

 Bank, with a depth of only 36 fathoms, and the Milne Bank, with 

 81 fathoms, both about 550 miles from Newfoundland, which is the 

 nearest continental land. Other instances are the Josephine Bank, 

 with 82 fathoms, and Gettysburg Bank, with 30 fathoms, the 

 distance of the former from Cape St. Vincent being 250, and the 

 latter 130 miles, with intermediate depths of from 1700 to 2500 

 fathoms. The soundings in the ' Bulldog ' Expedition also gave 

 748 between 1168 and 1260 fathoms, and the 'Valorous' soundings 

 gave 690 between 1450 and 1230 fathoms in another part of the 

 North Atlantic and very far from any land. 



A glance at the large series of the diagrams of the ' Challenger ' 

 soundings will at once serve to convince any one of the extreme un- 

 evenness of the sea-bottom everywhere in the Atlantic and Pacific 

 oceans. It would be difiicult to find a greater degree of unevenness 

 in any diagrams of the earth's surface, the total extent of which 

 scarcely exceeds one-fourth of that of the sea. 



Diagrams to illustrate the inequalities of the sea-bottom in the 

 case of the telegraph cable, and the iiTCgularities of level in a 

 similar extent of land in the Perthshire Highlands, are placed 

 before you. 



9. Deposits. 



The floor of the ocean is covered by a more or less thick layer of 

 ooze or mud, and clays of different sorts and colours, and is in- 

 habited by various animals. One of these deposits is called " Glohi- 

 gerina-ooze,''^ and is widely distributed over the bed of both the 

 Atlantic and the Pacific. Another deposit is called "Red Clay," 

 and is found at depths exceeding 2000 fathoms. Mr. Murray, one 

 of the ' Challenger ' naturalists, has carefully worked out the deep- 

 sea deposits which were observed and collected during the expe- 

 dition. According to him the Glohigerina-ooze occurred in the 

 North Atlantic at forty-nine stations, from depths of between 780 



