H. W. Pearson—Changes in the Sea-Level. 121 
Babinet, was compelled to invoke a recent diminution in the Gulf 
Stream to explain the progressive protrusion of the entire northern 
hemisphere above the level of the sea during the last three centuries. 
Other changes in direction or velocity have been either actually 
observed or inferred from indirect evidence. 
Humboldt informs us that a current near the Bahamas flowed to the 
south-east in 1787. It now flows to the north-west at a velocity of 
26 miles a day. 
Repeated statements have been made that at different times in the 
past the fish (cod or herring) industry, off the coasts of Ireland, 
Scotland, Denmark, and France, has been ruined or injured by the 
migrations made necessary by the diversions of ocean currents. 
Dr. Bessel has shown that the currents of Davis Straits formerly 
ran in an opposite direction. Reclus has shown also that during the 
Tertiary period the Gulf Stream along the coast of Cuba had direction 
differing from that of the present. 
It will be admitted that the citations above given in no case seem 
conclusive. They are mostly deductions made by those who have 
otherwise been unable to explain observed phenomena. Nevertheless, 
the established positions of many of those who have drawn these 
conclusions and the profound respect we entertain for their judgment 
should warrant us in accepting their decisions as most certainly 
probable. 
We may adopt, therefore, as most reasonable, even if not yet firmly 
established, the following proposition:—Variation and diversion of 
ocean currents have certainly occurred in the past. It is probable 
that these changes may be going on to-day, and it is certain we must 
expect them in the future. 
Now, then, it seems a mathematical certainty that if either variation 
or diversion in flow of ocean currents takes place the surface-levels on 
all coastlines must change in due proportion, and that these changes 
must necessarily be in opposite directions in not distant locations. 
It thus appears that Playfair’s law, unchallenged for a century, has 
during all this time occupied a position to which it had no title. 
During the full lifetime of the science of geology we have been 
utilizing the apparent motions in the earth’s crust herein considered 
as types, as living illustrations, of that uplifting of continents, that 
slow growth in mountain chains, required by our modern doctrines. 
Playfair’s theory has thus, by its absolute and unquestioned 
acceptance during this long period, put bar upon progress. No man 
had courage to question its correctness, therefore no man had occasion 
to seek other explanation. Now, however, the argument so long 
unassailable fails us; we find it weak, erroneous, impotent, and when 
we look back over our recent geologic pathway and see how much we 
have built upon this frail foundation, upon this uncertain inference 
of a plastic and mobile crust, one is tempted to ask how can such 
building be stable? How can such superstructure be more enduring 
than its supporting fabric ? 
