790 REPORT—-1899. 
methods employed in deep-sea observations. The most profound abysses of the 
ocean are now being everywhere examined by sailors and scientific men with 
increasing precision, rapidity, and success. 
The recognition of oceanography as a distinct branch of science may be said to 
date from the commencement of the Challenger investigations. The fuller knowledge 
we now possess about all oceanic phenomena has had a great modifying influ- 
ence on many general conceptions as to the nature and extent of those changes 
which the crust of the earth is now undergoing and has undergone in past geological 
times. Our knowledge of the ocean is still very incomplete. So much has, how- 
ever, already been acquired that the historian will, in all probability, point to the 
oceanographical discoveries during the past forty years as the most important 
addition to the natural knowledge of our planet since the great geographical 
voyages associated with the names of Columbus, Da Gama, and Magellan, at the 
end of the fifteenth and the beginning of the sixteenth centuries. 
It is not my intention on this occasion to attempt anything like a general 
review of the present state of oceanographic science. But, as nearly all the samples 
of marine deposits collected during the past thirty years have passed through my 
hands, I shall endeavour briefly to point out what, in general, their detailed exami- 
nation teaches with respect to the present condition of the floor of the ocean, and I 
will thereafter indicate what appears to me to be the bearing of some of these 
results on speculations as to the evolution of the existing surface features of our 
planet. 
Depth of the Ocean. 
All measurements of depth, by which we ascertain the relief of that part of 
the earth’s crust coyered by water, are referred to the sea-surface ; the measure- 
ments of height on the land are likewise referred to sea-level. It is admitted 
that the ocean has a very complicated undulating surface, in consequence of the 
attraction which the heterogeneous and elevated portions of the lithosphere 
exercise on the liquid hydrosphere. In the opinion of geodesists the geoid may 
in some places depart from the figure of the spheroid by 1,000 feet. Still it is not 
likely that this surface of the geoid departs so widely from the mean ellipsvidal 
form as to introduce a great error into our estimates of the elevations and de- 
pressions on the surface of the lithosphere. 
The soundings over the water-surface of the globe have accumulated ai a rapid 
rate during the past fifty years. In the shallow water, where it is necessary 
to know the depth for purposes of navigation, the soundings may now be spoken of 
as innumerable; the 100-fathom line surrounding the land can therefore often be 
drawn in with much exactness. Compared with this shallow-water region, the 
soundings in deep water beyond the 100-fathom line are much less numerous; 
each year, however, there are large additions to our knowledge. Within the 
last decade over ten thousand deep soundings have been taken by British ships 
alone. The deep soundings are scattered over the different ocean-basins in varying 
proportions, being now most numerous in the North Atlantic and South-west 
Pacific, and in these two regions the contour-lines of depth may be drawn in with 
greater confidence than in the other divisions of the great ocean-basins. It may 
be pointed out that 659 soundings taken quite recently during cable surveys in the 
North Atlantic, although much closer together than is usually the case, and yield- 
ing much detailed information to cable engineers, have, from a general point of 
view, necessitated but little alteration in the contour-lines drawn on the Challenger 
bathymetrical maps published in 1895. Again, the recent soundings of the 
German s.s. Valdivia in the Atlantic, Indian, and Southern Oceans have not caused 
very great alteration in the positions of the contour-lines on the Challenger 
maps, if we except one occasion in the South Atlantic when a depth of 2,000 
fathoms was expected and the sounding machine recorded a depth of only 536 
fathoms, and again in the great Southern Ocean when depths exceeding 3,000 
fathoms were obtained in a region where the contour-lines indicated between 1,000 
and 2,000 fathoms. This latter discovery suggests that the great depth recorded 
by Ross to the south-east of South Georgia may not be very far from the truth, 
