William Benjamin Carpenter

“ The annual isotherms, which cross the Sargasso Sea with nearly regular parallelism, and on the African side tend somewhat to the south, where they meet the colder water of the North African Current, show a strong northward bend on the American side, along the early course of the Gulf Stream ; but as its excess of temperature above that of the Atlantic generally diminishes as we trace it towards the Banks of Newfoundland, this northward deflection progres sively becomes less. ”

“ Guided by the principle that great oceanic basins are to be considered rather as original marine areas that have been limited by the elevation of their boundaries, than as having been formed by the excavation of terrestrial areas, we have to inquire what evidence there is that the basin of the Atlantic has undergone any considerable change within a compara tively recent period. ”

“ Not only is the proportion of the laud-surface of the globe to its water- surface scarcely more than one-third (being as 1 to 2 78) , but the entire mass of the land which thus covers little more than one-fourth of the surface of the globe is quite insignificant in comparison with that of the water which covers the remaining three-fourths. ”

“ For it is now generally admitted that these icebergs are really parts of glaciers, that were originally formed on the mountain-slopes of Greenland and Labrador, and then descended valleys which open out on their coasts, so as, on arriving at the mouths of these valleys, to detach themselves and float away, being borne southwards by the Polar Current to be presently described. Most Arctic icebergs of which a near view can be obtained are observed to have upon them a considerable number of pieces of rock, sometimes of a very considerable size ”

“ Now on the surface of this deposit there have been found so many living types, especially belonging to the groups of Echinoderms, Corals, Siliceous Sponges, and Foraminifera, which closely correspond with types hitherto regarded as characteristic of the Cretaceous, epoch, that the question naturally suggests itself whether the existing are not the lineal descendants of the fossil types, the differences they present being not greater than may be fairly attributed to the prolonged action of differences of temperature, food, pressure, &c. ”

“ For a dis tance of about 230 miles to the westward of Ireland there is a slope of only about 6 feet in a mile ; but in the next 20 miles there is a fall of 9000 feet, after which there is little change of level for 1200 miles. Hence as the depth of the sea immediately surrounding the British Isles is nowhere 100 fathoms (so that an elevation of their whole area to that amount would unite these islands not only to each other but also to the continent of Europe) , it is obvious that the platform on which they rest is really, although now submerged, a part of the land-mass of Europe. ”

“ Depressions of 1000 feet would submerge large areas of the existing land; but fifteen times as much movement would be required to convert such land into an ocean of average depth, or to cause an ocean three miles deep to replace any one of the existing continents. ”

“ But since the course of Dr Petermann s isotherms shows that the north ward flow extends across the whole breadth of the Atlantic between Newfoundland and the British Isles a distance of about 2000 miles we are required to believe that a rivulet (for such it is by comparison) of 60 miles breadth and 100 fathoms depth (see section, fig. 5) , of which the greater part turns southwards round the Azores, and of which the remainder is flowing due east when we last recognise it, is able to impart a northerly movement to a stratum of 2000 miles in breadth, and at least 600 fathoms depth. ”

“ The distribution of marine plants seems mainly deter mined by light, temperature, and depth, a further influence being exerted by the character of the shores. The diminu tion of liyht iu its passage through sea-water is so rapid, that the quantity which penetrates to a depth of 250 or 300 fathoms may be regarded as almost infinitesimal ; and in conformity with this we find a very rapid diminution of Algal life below the depth of 100 fathoms. ”

“ Putting aside the older soundings as utterly untrust worthy, and accepting only those taken by the modern methods, whose reliability has been amply tested by the accordance of diversified experiences, we can now assert with confidence that scarcely any portion of its floor has a depth exceeding 3000 fathoms, or about 3 "4 miles, the greatest depth determined by the recent "Challenger" sound ings, which was that of a limited depression about a hundred miles to the north of St Thomas, having been 3875 fathoms, or about 4 4 miles. ”

“ The marked contrast in temperature which is often there exhibited between two contiguous bands of water, a thermometer hanging from a ship s bow show ing a temperature of 70, whilst another hanging from the stern shows only 40, is due not so much to the elevation produced by the Gulf Stream as to the depression produced by the Arctic Current. ”

“ A series of tempera ture-soundings taken along the west of Ireland, the Bay of Biscay, and the coast of Portugal, confirmed him in this view, by showing that the division between an upper warm stratum and a cold under-stratum exists in the North Atlantic at a depth of from 700 to 900 fathoms, the whole mass of water below this having either flowed into the basin from the polar area, or having had its temperature brought down to from 39 to 3G 0- 5 by mixture with the polar inflow. ”

“ The upper stratum is occupied for the most part by the larger and coarser forms of the Fucaceoe, or olive-green sea-weeds, whilst the more delicate Ceramiactce, or red sea-weeds, fre quent deeper waters ; and, as it appears from experiments made in aquaria that the latter do not flourish in full light, but grow well in shadow, it may be concluded that their preference for a moderate depth is rather for reduced light and stillness than for depth per se. At a depth of 150 fathoms very few ordinary sea-weeds maintain their ground ”

“ The early defining, even in Archsean times, of the final features of North America, ;nid the con formity to one system visibly marked out in every event through the whole history in the positions of its outlines and the formations of its rocks, in the character of its oscillations, and the courses of the mountains from time to time raised sustain the statement that the American con tinent is a regular growth. ”

“ And a confirmation of this view is found in the fact, ascertained by recent soundings, that the deepest local depressions of the sea-bed are met with in the neighbourhood of islands that have been raised by volcanic agency. ”

“ These fossiliferous deposits have been subse quently elevated to heights of from 1500 to 2000 feet above the level of the sea, showing a rise of the base of the craters; progressive additions have been made to their upper part by the piling up of basaltic andtrachytic lavas. 1 That this state of activity still continues is proved by the fact that in 1811 a new island was temporarily formed in the Azores group, off St Michael, by the throwing-up of ashes, and the formation of a cone about 300 feet high, with a crater in the centre. ”

“ E. movement of a stratum of warm water sufficiently thick to retain a surface-temperature con siderably higher than that of the air above it is to be accounted fur. The solution of the problem seems to be afforded by the doctrine of a General Oceanic Circulation, sustained by opposition of temperature only, which was first distinctly propounded in 1845 by Professor Lenz of St Petersburg, on the basis of observations made by him during the second voyage of Kotzebue (1825-1828) . ”