The Present Condition of the Latitude Problem . 
231 
however, stands in the way of this explanation. Mr. Chandler has in¬ 
dicated as a result of his investigation that the period of time within 
which the latitude makes a complete oscillation is not of uniform length 
hut ranges from about 350 up to 427 days, and this variation in the length 
of the period is in no way accounted for by Newcomb’s explanation. 
Turning now for a moment aside from this periodic variation of the 
latitude, let us briefly consider another but allied phase of the same 
matter. At the conference of the International Geodetic Association, 
held at Home in 1884, Fergola, an Italian astronomer, presented a con¬ 
siderable amount of data tending to show that during the past century 
there had been a progressive diminution in the latitudes of European 
observatories. In other words, that aside from this periodic variation of 
latitudes there had been a steady and uniform drift of the surface of 
the earth in Europe away from the north pole. Fergola’s paper at¬ 
tracted great interest at the time, and his suggestion that a concerted 
plan of action should be adopted for the systematic investigation of this 
secular change in latitude was adopted by the Geodetic Association. 
Measures were taken to have a series of observations for this purpose 
commenced at Washington and at Lisbon; but unfortunately the mat¬ 
ter terminated without anything having been accomplished and the 
plan for systematic investigation seems to have been abandoned. 
At the earnest request of some geologists especially interested in gla¬ 
cial phenomena, I took up the question of the secular variation of lati¬ 
tudes anew some three years ago, with the intention of examining more 
carefully the American data, which had scarcely been touched upon by 
Fergola, and of ascertaining whether it could be made to yield any con¬ 
tribution to a better knowledge of the secular change. Without going 
into the details of this investigation, it may suffice to state here that this 
data, although somewhat scanty in amount, still indicates very strongly 
that American observatories have a common motion toward the north 
pole amounting to about four feet per year; in other words, that the 
rotation axis of the earth, instead of being fixed relatively to the crust of 
the earth, is changing its position, moving in a direction along the west 
coast of Greenland, so that it is being brought progressively nearer to 
American stations and carried more slowly away from European ones. 
The results of this investigation were presented last summer to the 
American Association for the Advancement of Science, and a committee 
of that association was appointed to devise means for further investiga¬ 
tion of these changes in latitude, both periodic and secular. Under the 
auspices of the International Geodetic Association, simultaneous obser¬ 
vations are now being made in Germany and in the Hawaiian Islands. 
These will suffice for a very accurate determination of the periodic 
changes of latitude, but they are not well adapted to a determination of 
the secular change, the longitudes being badly chosen for this purpose, 
