526 
in one place; through the agency of winds, quartz sand is 
heaped up in another; through the agency of water, beds of 
clay, of oxides of iron and of manganese are spread out in 
other directions. 
The contraction of the centrosphere supplies the force which 
folds and crumples the lithosphere. The combined effect of 
hydrosphere, atmosphere and biosphere on the lithosphere 
gives direction and a determinate mode of action to that force. 
From the earliest geological times the most resistant dust of the 
continents has been strewn along the marginal belt of the sea- 
floor skirting the land. At the present time, the deposits over 
this area contain on the average about 70 per cent. of free and 
combined silica, mostly in the form of quartz sand. In the 
abysmal deposits far from land there is an average of only about 
30 per cent. of silica, and hardly any of this in the form of 
quartz sand, Lime, iron and the other bases largely pre- 
dominate in these abysmal regions. The continuous loading on 
the margins of the emerged land by deposits tends by increased 
pressure to keep the materials of the tektosphere in a solid con- 
dition immediately beneath the loaded area. The unloading of 
emerged land tends by relief of pressure to produce a viscous 
condition of the tektosphere immediately beneath the denuded 
surfaces. Under the influence of the continuous shakings, 
tremors and tremblings always taking place in the lithosphere, 
the materials of the tektosphere yield to the stresses acting on 
them, and the deep-seated portions of the terrigenous deposits 
are slowly carried towards, over or underneath the emerged 
land. The rocks subsequently re-formed beneath continental 
areas out of these terrigenous materials, under great pressure 
and in hydrothermal conditions, would be more acid than the 
rocks from which they were originally derived, and it is well 
‘known that the acid silicates have a lower specific gravity than 
the intermediate or basic ones. By a continual repetition of 
this process the continental protuberances have been gradually 
built up of lighter materials than the other parts of the litho- 
sphere. The relatively light quartz, which is also the most 
refractory, the most stable and the least fusible among rock- 
forming minerals, plays in all this the principal vé/e. The 
average height of the surface of the continents is about three 
miles above the average level of the abysmal regions. If now 
we assume the average density of the crust beneath the 
continents to be 2°5, and of the part beneath the abysmal regions 
to be 3, then the spheroidal surface of equal pressure—the 
tektosphere—would have a minimum depth of eighteen miles 
beneath the continents and fifteen miles beneath the oceans, or 
if we assume the density of the crust beneath the continents to 
‘be 2°5, and beneath the abysmal regions to be 2°8, then the 
tektosphere would be twenty-eight miles beneath the continents 
and twenty-five miles beneath the oceans. The present 
condition of the earth’s crust might be brought about by the 
disintegration of a quantity of quartz-free volcanic rock, 
covering the continental areas to a depth of eighteen miles, and 
the re-formation of rocks out of the disintegrated materials. 
Where the lighter and more bulky substances have 
accumulated there has been a relative increase of volume, and 
in consequence bulging has taken place at the surface over the 
continental areas. Where the denser materials have been laid 
down there has been flattening, and in consequence a depres- 
sion of the abysmal regions of the ocean-basins. It is known 
that, as a general rule, where large masses .of sediment have 
been deposited, their deposition has been accompanied by a 
depression of the area. On the other hand, where broad 
mountain platforms have been subjected to extensive erosion, 
the loss of altitude by denudation has been made good by a rise 
of the platform. This points to a movement of matter. on to 
the continental areas. 
If this be anything like a true’ conception of the interactions 
that are taking place between the various geospheres of which 
our globe is made up, then we can understand why, in the 
gradual evolution of the surface features, the average level of 
the continental plains now stands permanently about three 
miles above the average level of those plains which form the 
floor of the deep ocean-basins. We may also understand how 
the defect of mass under continents and an excess. of mass 
under the oceans have been brought about, as well as deficiency 
of mass under mountains and excess of mass under plains. Even 
the local anomalies indicated by the plumb-line, gravity and 
magnetic observations may in this way receive a rational 
explanation. It has been urged that an enormous time—greater 
even than what is demanded by Darwin—would be necessary for 
NO. 1561, VOL. 60] 
NATURE 
[SEPTEMBER 28, 1899 
an evolution of the existing surface features on these lines. I 
do not think so. Indeed, in all that relates to geological time I 
agree, generally speaking, with the physicists rather than with 
the biologists and geologists. 
Progress of Oceanic Research. 
Ihave now touched on some of the problems and speculations 
suggested by recent deep-sea explorations ; and there are many 
others, equally attractive, to which no reference has been made. 
It is abundantly evident that, for the satisfactory explanation of 
many marine phenomena, further observations and explorations 
are necessary. Happily there is no sign that the interest in 
oceanographical work has in any way slackened. On the con- 
trary, the number of scientific men and ships engaged in the 
study of the ocean is rapidly increasing. Among all civilised 
peoples and in all quarters of the globe the economic importance 
of many of the problems that await solution is clearly 
recognised. 
We have every reason to be proud of the work continually 
carried on by the officers and ships attached to the Hydro- 
graphic Department of the British Navy. They have surveyed 
coasts in all parts of the world for the purposes of navigation, 
and within the past few years have greatly enlarged our know- 
ledge of the sea-bed and deeper waters over wide stretches of 
the Pacific and other oceans. The samples of the bottom 
which are procured, being always carefully preserved by the 
officers, have enabled very definite notions to be formed as to 
the geographical and bathymetrical distribution of marine 
deposits. 
The sh ps belonging to the various British telegraph cable 
companies have done most excellent work in this as well as in 
other directions. Even during the present year Mr. R. E. 
Peake has in the s.s. Srz¢annza procured 477 deep soundings in 
the North Atlantic, besides a large collection of deep-sea 
deposits, and many deep-sea temperature and current 
observations. 
The French have been extending the valuable work of the 
Talisman and Travailleur, while the Prince of Monaco is at 
the present moment carrying on his oceanic investigations in the 
Arctic Seas with a large newJyacht elaborately and specially fitted 
out for such work. The Russians have recently been engaged 
in the scientific exploration of the Black Sea and the Caspian 
Sea, and a special ship is now employed in the investigation of 
the Arctic fisheries of the Murman coast under the direction of 
Prof. Knipowitsch. Admiral Makaroff has this summer been 
hammering his way through Arctic ice, and at the same time 
carrying on a great variety of systematic observations and 
experiments on board the Yerrak—the most powerful and most 
effective instrument of marine research ever constructed. Mr, 
Alexander Agassiz has this year recommenced his deep-sea 
explorations in the Pacific on board the U.S. steamer A/batross. 
He proposes to cross the Pacific in several directions, and to 
conduct investigations among the Paumotu and other coral 
island groups. Prof. Weber is similarly employed on board a 
Dutch man-of-war in the East Indian Seas. The Deutsche 
Seewarte at Hamburg, under the direction of Dr. Neumayer, 
continues its praiseworthy assistance and encouragement to all 
investigators of the ocean, and this year the important German 
Deep-Sea Expedition, in the s.s. Va/divéa, arrived home after 
most successful oceanographical explorations in the Atlantic, 
Indian and Great Southern Oceans. 
The Be/gica has returned to Europe safely with a wealth of 
geological and biological collections and physical observations, 
after spending, for the first time on record, a whole winter 
among the icefields and icebergs of the Antarctic. Mr. 
Borchgrevink in December last again penetrated to Cape Adare, 
successfully landed his party at that point and is now winter- 
ing on the Antarctic continent. The expeditions of Lieut. 
Peary, of Prof. Nathorst, of Captain Sverdrup, and of the Duke 
of Abruzzi, which are now in progress, may be expected to 
yield much new information about the condition of the Arctic 
Ocean. Mr. Wellman has just returned from the north of 
Franz Josef Land with observations of considerable interest. — 
Some of the scientific results obtained by the expeditions in 
the Danish steamer golf have lately been published, and 
these, along with the results of the joint work pursued for 
many years by the Swedes, Danes and Norwegians, may 
ultimately have great economic value from their direct bearing 
on. fishery problems and on weather forecasting over long 
periods of time. 
