CHARLES B. WARRING. 89 
duce zj> of a second change in the Pole during half a 
century, the presumption would seem to be against such 
a fixity. 
The question appears to be still an open one. Till it 
is settled that the latitude is changing, it would seem 
premature to speculate upon the cause of the movement, 
yet it may not be out of place to inquire what force 
exists that could produce such an effect. 
Mr. Petrie, as quoted above, speaks of the influence of 
ocean currents, or, as he styles it, the great oceanic circu- 
‘lation. It is difficult to see how that could affect the 
latitude. Since every current has its opposite current, 
the eastward effect would be neutralized by the westward 
and the tendency to increase the latitude—if it exists— 
meets its counterpart in a tendency to diminish it. 
It is well known that there are now and have always 
been movements in the earth’s crust, caused by its cool- 
ing and contracting. The most evident effect of these 
now are the elevations and depressions going on at the 
present time in various parts of the world, as in Norway, 
Italy, the eastern coast of the United States, and else- 
where. There were horizontal movements in the past, 
shown by the folding of the strata, and by the sliding 
of the strata one over the other: The very uprisings are 
in general, due to lateral pressure and consequent move- 
ment. It is quite certain that from this cause every part 
of the earth’s crust has at some time changed either its 
latitude, or longitude, and probably both. This cause 
is still active, hence it is more than probable that many 
places on the earth are slowly carried either towards or 
from the equator. If Pulkowa happens to be on a part 
of the earth’s crust that is being pushed southward, say 
a foot in a year, then its change of latitude is easily ac- 
counted for. If Greenwich happens to be on a part of 
the crust where these forces are at present inactive, then 
3g 
