DYNAMICAL GEOLOGY 
83 
measurable under usual conditions and with the ordinary means 
of evaluation at our command. 
Only under especially favorable circumstances could first clues 
to such phenomena become discernible. Only on some great plains 
tract which had long been free from the effects of mountain 
making activities could proper conditions of measurement obtain. 
Even with the most refined instruments, with comparisons of 
results of observations extending over a period outspanning a 
human life would appreciable returns appear. The physical dif¬ 
ficulties of solution seem so great as to prohibit any systematic 
initiation of proper measurements even if it were desired to seek 
only rough estimates. 
Actual instrumental measurements of a stretching crust recently 
come from an unexpected quarter. It may be that they are the 
very proofs so long sought. Until the same are shown to be 
something to the contrary it may be safely assumed that they 
afford possible and concrete evidences of polar bulging and chang¬ 
ing sphericity demanded by a constantly diminishing rate of the 
earth’s rotation. This desideratum hails from Denmark. 
In the recent application of the refined Jaderin apparatus to 
the Copenhagen base-line, upon which the triangulation of Den¬ 
mark fundamentally depends, the Coast and Geodetic Survey 
of that country found that the initial measurement was 51 mille- 
meters more than the figures of the old determination made by 
Schumacher in 1838, to which all calculations had been so long 
referred. So disconcerting was this discrepancy that the Pots¬ 
dam auxiliary base was measured and compared no less than 
ten times. A new Danish base was also established and its length 
adjusted to the old Copenhagen base. As a result the figures 
of 1838 were accepted as essentially correct; and the length of 
the Copenhagen base-line was proved to have appreciably length¬ 
ened during‘a specified period of about three-quarters of a cen¬ 
tury.^ 
The feature of great interest in the present connection is the 
nearness of agreement between the observed amount of lengthen¬ 
ing of a refinely measured line such as the Copenhagen base in 
80 years, and the theoretically calculated stretching of a segment 
1 Den Danske Gradmaaling, No. 15, Nye Basismaalinger i Danmark, 88 pp., 
Copenhagen, 1916 
