GENERAL MEETING. 19 
actual measure of compression indicated by the average degrees of 
plication of the stratified rocks. Supposing these to represent a 
a reduction from the original circumference of the crust of one-eley- 
enth, this would involve a former excess of volume of about one- 
third. 
The speaker then gave an historical sketch of the growing con- 
viction among physicists that from the tidal retardation of the 
earth’s rotation, the length of the day must have been much shorter 
in remote geological eras than at present—and consequently the ob- 
lateness of the terrestrial ellipsoid considerably greater. Estimating 
that a day of six hours would give an equatorial enlargement of about 
one-tenth (without taking any account of volumetric change by reduc- 
tion of temperature), he thought this morphologic change an adequate 
explanation of the.observed crumpling of the earth’s crust; and 
claimed that the cause assigned is both a true and a sufficient one. 
This larger oblateness would imply an equatorial bulge 396 miles 
greater in radius than the present ; and a corresponding depression 
of the poles 658 miles below their present levels. As in a general 
way confirmatory of this hypothesis, Guyot’s statement was quoted 
that “On the whole, the reliefs begin with the vast, low plains 
around the polar circle, and go on increasing from the shores of the 
Arctic ocean toward the tropical regions;” and that “the ocean 
basins become less deep toward the - = A pci as the lands 
become lower toward the same region.” 
[This paper is printed in full in the American Journal of Science, 
3d Series, Vol. XXX, pp. 249-266.] 
272ND MEETING. JUNE 6, 1885, 
The President in the Chair. 
Twenty-eight members present. 
Mr. J. P. Ipprnes made a communication on 
THE COLUMNAR STRUCTURE IN THE DIABASE OF ORANGE 
MOUNTAIN, N. J. 
[ Abstract. ] 
The paper describes the occurrence and structure of the “ trap” 
rock in the neighborhood of Orange, with special reference to the 
arrangement of the columns in John O’Rourke’s quarry and in the 
