OROGENY AND EARTH’S ROTATION 
57 
figure, perhaps one having twelve, or twenty-four, faces. That 
the rhombic dodecahedron is probably the real form, if there be 
any, although having in nature curved faces, seems to be borne 
out by the disposition of the principal mountain ranges of the 
world, and by the situation of the main volcanic centers at the 
sharp solid angles or the points where each set of three faces 
intersect. 
Collapsing effects in ordinary solids give clue as to what to ex¬ 
pect in nature. Considering for the moment only cases of two 
dimensions, crowded circles, or cylinders, as in the honey-comb, 
pass over to six-sided figures. Contraction of cooling lava-sheets 
break the mass up into hexagons, of which the Giant’s Causeway, 
or Fingal’s Cave, in Ireland, are only famous examples. Wheth¬ 
er the stress comes from within or without the pressure-figure is 
the same. Taking up the problem in three dimensions the crowd¬ 
ing of balls produces a twelve-sided form, or the rhombic dode¬ 
cahedron ; a collapsing spheroid would necessarily have a tendency 
to approach a similar form. 
Recent laboratory experiments on the faceted form of a collaps¬ 
ing spheroid invariably give rhombic faces.^® These tests are 
made with heavy roll-paper such as modern newspapers use. The 
amount of collapse is measured by the diurnal variation in the 
humidity of the air. On wet days the paper swells; on dry days 
it contracts, leaving a surface of singularly large and perfect 
rhombohedrons. By use of materials not so tough relatively, or 
by the selection of some brittle substance, it is probable that rup¬ 
ture would take place along the edges of the facets. In all prac¬ 
tical respects the chief lines of mountain upheaval on the earth 
are exactly located in miniature. 
The primal shortcoming which the contractional hypothesis pre¬ 
sents is the restriction of such expression as crustal shortening 
to geologic processes which are at best now recognized as moot 
forces. In the 300 years that have elapsed since Rene Descartes 
set forth his fancies, conceptions of world forces have materially 
shifted position and the point of view of the earth student has 
changed. Logically the old reasoning is from analogy rather than 
from cause to effect, or from process to product. In the begin¬ 
ning, when gravity was the only apparent force upon which spec- 
18 Bull. Geol. Soc. America, Vol. XXIX, p. 76, 1918. 
