Sept. 28, 1876] 



NA TURM 



493 



observations brought out by increased experience, and reached 

 England on May 24, 1876. 



The cruise on the whole has been singularly fortunate, 

 and it has only been in very unusual circumstances that v?e 

 have been prevented by the v\reather from doing our work. 

 The health of the party has been exceptionally good, and 

 the loss by death small. Two misfortunes only befell us 

 in any way sufficiently grave to affect the success ot the 

 expedition — one was the death of one of the most zealous 

 and most promising of our civilian staff, Dr. von Wille- 

 moes-Suhm, which for long through a gloom over our little 

 party ; and the other was the recall of Capt. Nares to take 

 command of the Arctic Expedition. Capt. Nares had acquired, 

 to a remarkable degree, the esteem and confidence of all on 

 board, and although we could not but feel that no other selection 

 of a leader for the Arctic Expedition could have been made in 

 any way so satisfactory, still the fact remained that by the loss 

 of his experience we were greatly crippled. We all trust that 

 he and his bold companions may now be in safety and nearing 

 the goal of their hazardous enterprise ; and I am sure that, with 

 the exception of his wife and children, none so earnestly pray 

 for his welfare as his old comrades of the Challenger. 



Before endeavouring to sketch one or two of the general re- 

 sults at which we have arrived, I wish to give a few words of 

 explanation. I shall have to bring before you various matters 

 which to you may appear novel, but many of these are not en- 

 tirely original — many have been shrewdly hinted orguessed at from 

 time to time, and many isolated observations have furnished clues 

 which have been eagerly seized by students and made the bases 

 of speculations more or less touching the truth. It is only the 

 unexampled opportunity which we have had at our command 

 which now enables us to place them before you in a connected 

 form, and with a completeness which in some directions at all 

 events precludes the possibility of grave error. It would be im- 

 possible for me on this occasion to acknowledge individually the 

 debts we owe to our predecessors, but I must do so in one or 

 two instances. The American Coast Surveyors commenced this 

 work about the same time that we did, and their results are of 

 the greatest possible value. I have only lately become acquainted 

 with a most thoughtful and suggestive paper by Prof. William- 

 son, which was published so far back as 1847, in the Transac- 

 tions of the Manchester Philosophical Society, in which the origin 

 of organic deposits— one of the most important points which we 

 have to consider — was worked out with great care and skill. In 

 1869, 1870, and 1 87 1 the observations made in the Lightning, 

 Porcupine, and Sheerwater completely revolutionised our ideas of 

 many of the questions involved. I shall not, however, consider 

 it necessaiy to quote continually the speculations of my colleague, 

 Dr. Carpenter, on the physics of the ocean, to which, however 

 widely I may differ from his conclusions, I attach a high value ; 

 nor the investigations of Mr. Gwj'n Jeffreys on the distribution of 

 marine animal forms ; for these two gentlemen must be regarded 

 as members of the firm. Among the many points of interest 

 which engaged our attention there were three more especially 

 prominent, and, if possible, I will confine myself to these three, 

 so as to bring my work within a certain limit. The first of these 

 the contour of the bottom and the nature of the deposits now 

 being formed upon it ; the second is the more difficult question 

 of the distribution of deep-sea climate ; and the third, which is 

 perhaps the most interesting and curious, is the nature and dis- 

 tribution of the peculiar races of animals which are now found 

 at the bottom of the sea. I shall take up these three points in 

 succession, and endeavour very briefly to give an idea of the 

 condition of knowledge with regard to them when the Challenger 

 started, and the light which her observations have been enabled 

 to throw upon them. 



I need scarcely go into great detail with regard to the contour 

 of the bottom, for the question is mainly a hydrographic one, 

 and would involve use of numbers which would be scarcely suit- 

 able for a public lecture. As I have said already, the average 

 depth of the ocean is somewhere about 2,000, or probably 2,500 

 fathoms. A very large portion of the ocean haSj a depth some- 

 what less than this, and a depth of 2,000 fathoms appears to be 

 common. Where it is 2,500 or 3,000, we would appear to be 

 going into submarine valleys, with the exception of the North 

 Pacific, where there is an enormous extension of water of great 

 depth, in many cases going beyond 3,000 fathoms. In the 

 AUantic, a great part of the northern portion has a depth of 

 about 2,000 fathoms, with a middle ridge which passes down 

 firom Greenland, and includes the various groups of islands and 

 single islands to Tristan d'Acunha, and probably beyond it. In 



the South Atlantic, on each side of this ridge, which is there 

 called the "Dolphin Rise," in compliment to the American ship 

 which first surveyed it, there is a trough which runs to a con- 

 siderable depth, usually down to 3,000 fathoms, and these form 

 marked depressions roughly parallel with the axes of the South 

 American and African continents. I will frequently allude to 

 the Atlantic, as I have no time to enter into detail with regard 

 to the rest of the seas, and we had the best opportunity of 

 working it. Now, the bottom of the sea is covered with certain 

 deposits. The whole bottom of the sea, so far as we are aware, 

 is gradually receiving certain accumulations, and these accumu- 

 lations are giving rise to formations which we look upon as the 

 rocks of the future. We know by our knowledge of the science 

 of geology that the whole dry land, as we have it at present, is 

 composed — with the exception of certain volcanic rocks, which 

 may be, in many cases, metamorphosed sedimentary rocks — of 

 stratified beds laid down at the bottom of the sea. We know 

 that the material of these beds is to a certain extent derived from 

 the gradual disintegration of the land, and we look upon the sea 

 as the great restorer of the solid material which is to form future 

 islands and continents, as the bottom of the sea becomes raised 

 up at some future time above the level of the ocean. Now, the 

 whole of the sea-bottom is receiving these deposits, and it was 

 one of our great objects in the cruise of the Challenger to deter- 

 mine what these deposits are, under what laws they are being 

 laid down, and what the relation of these modem deposits may 

 be to the ancient deposits, which form the solid crust of the 

 earth. We were well aware that there was a perpetual disin- 

 tegration of the land going on by rivers and by the action of the 

 sea round its coasts, and that the material worn off the land was 

 being carried away by the ocean and laid down at some distance 

 from the land, and that the material was being selected and 

 arranged according to some definite laws. Accordingly, when 

 we came to test this, we were not surprised to find that the 

 debris of the land extended for some hundreds of miles from the 

 land out to sea. We found clays being formed, and various 

 deposits, differing according to the material from which they 

 were derived, and mixed up with the debris of animals living |in 

 the places where these deposits were being laid down. Within 

 a certain distance of the land we found the deposits formed to a 

 great extent of this peculiar shore material. 



Many years ago it was determmed by observation, even pre- 

 vious to the soundings for the first Atlantic cable, that over a 

 great part of the North Atlantic a very remarkable deposit was 

 being laid down — a deposit now known as Globigerma ooze. 

 This deposit consists of the shells of minute Foraminifera, princi- 

 pally belonging to one genus — the genus Globigerina. This, as 

 we found it in these deposits, was a small chambered shell ex- 

 tremely minute, about a millimetre in diameter, and these shells 

 were found in enormous quantity. When dry, the ooze was 

 something like fine sago, with little round shells falling from one 

 another, and showing that the deposit was formed almost entirely 

 of such shells. Some other genera were mixed with them, but 

 the great mass were Globigerince. When we took up by any 

 means material a little below the surface of the sea-bottom we 

 found the Globigerina shells were becoming broken and com- 

 pacted together so as to form a close and nearly amorphous mud, 

 in which there were very many complete Globigerina and many 

 pieces of the same. The whole of this deposit was composed 

 almost entirely of carbonate of lime, and the only rock which 

 this could possibly form was a limestone. It therefore appeared 

 that over a very large portion of the North Atlantic, and over 

 many other parts of the world where these observations had been 

 made, this limestone was being laid down. Further observations 

 showed that the chalk was composed lOf very nearly the same 

 material, and the analogy between these modem formations and 

 the chalk became very apparent. During the voyage of the 

 Challenger we had many opportunities of bringing up this modem 

 chalk, and the question which was always before our minds was 

 one which had been mooted before we started — Where did these 

 creatures live — did they live upon the bottom of the sea? or did 

 they live on the surface, their shells falling to the bottom after 

 death ? Until lately none of these animals, or very few, had 

 been found alive upon the surface. It was our general impres- 

 sion that they lived on the bottom, where we found their dead 

 shells. Mr. Murray, one of my companions in the Chdltenger, 

 has paid particular attention to the structure of the material 

 brought up from the bottom — its composition, and the sources 

 from which it was derived. He worked the tow-net and the 

 sounding apparatus together during the voyage, and came to a 

 decided conclusion, one to which we are absolutely forced to 



