32 
POPULAR SCIENCE REVIEW. 
the existence of a barrier of land west of Ireland, extending 
southwards from Iceland, would cut off the warm current from 
the Gulf of Mexico and produce a boreal fauna in the sea, just 
as a considerable extension of land within the arctic circle 
would chill the climate of all northern European land, and 
bring down an icy cap to the Alps and Pyrenees. 
We have only to look at the soundings already made, and 
compare the facts determined as to the depth of the Atlantic, 
to see how easily a comparatively small change in the relative 
level of the sea bottom must, by influencing the bottom tem- 
perature, modify and entirely alter the nature of the deposits. 
For this purpose a glance at the annexed chart (see Plate) will 
be sufficient. It will there be seen that undulations along the 
central line of the Atlantic canal, must divert currents which 
now convey warm water into latitudes very near the Arctic 
circle, while corresponding undulations across the ocean would 
affect such currents very little. On the other hand, it is well 
known that the great land undulations in our hemisphere have 
been rather in a direction parallel to the equator than from 
north to south, so that as there is a volcanic axis from Iceland 
southwards towards the African coast, indicated sometimes by 
actual eruption and very frequently by earthquakes, the move- 
ments are on the whole at right-angles, tending to separate still 
further the eastern from the western hemisphere, as the northern 
part of the old world is already separated from the southern. 
Whatever may be the value of speculations of this kind, there 
can be no doubt of the necessity of further active explorations 
of the sea bottom, accompanied by observations of bottom and 
intermediate temperature in all seas. Hitherto the nortli 
Atlantic canal has alone been examined with any approach to 
system, and even there but a very small area has been looked at. 
The parts of this ocean to the south of the telegraph plat- 
form should be followed and soundings taken, with a view to 
discover the direction of the banks between which the warm 
stream runs towards the Arctic Ocean. Systematic search to 
connect, if possible, Iceland and the volcanic islands of the 
Atlantic off the coast of Africa, and thus to discover whether 
the fauna east and west of this line are identical, is greatly 
needed. A similar search northwards, following the warm 
channel in that direction, could not fail to yield important in- 
formation, while the pursuit of the cold current bringing ice- 
bergs to its southern extremity after crossing the Gulf Stream 
might yield results little anticipated. The whole subject is one 
full of interest and promising a long continuance of important 
discovery. There is ample field for all, and it is hardly possible 
to imagine a more noble use of the resources in the possession 
of some of our wealthy owners of steam yachts, than a systematic 
