436 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



at different times, but that it is probably Miocene, or Mid-Tertiary, 

 has deep significance. It places at once the gypsum and associated 

 Pink shales among true continental, or epirotic, deposits — accumu- 

 lations on dry land and entirely independent of sea, lake, or river. '"^ 



FACETED FORM OF A COLLAPSING SPHEROID 



Comparable with some of the work in the i3hysical, chemical and 

 engineering laboratories are some of the recent experimental in- 

 quiries initiated in geology in our state. It sometimes seems sirange 

 that in a prairie state like Iowa this laboratory experimentation 

 should take the trend of the larger problems in geotectonics. In a 

 line of research such as geology presents where the materials used 

 are so largely dependent upon the immediate surroundings the selec- 

 tion of a topic that rests not upon place, matter or method is a de- 

 cided novelty. Several widely different experiments have been re- 

 cently completed. 



In certain experiments lately performed in which heavy, rolled 

 paper was used, the amount of collapse is measured by the diurnal 

 change in the humidity of the air. On wet days the result is a 

 surface of singularly large and perfect rhombohedrons. With paper 

 not so tough relatively, or with the use of some brittle substance, no 

 doubt rupture would take place along the edges of the facets. In 

 all practical respects the lines of the great mountain upheavals of 

 the globe are exactly located. 



The application of the principles to teluric conditions is obvious. 

 It is not necessary to postulate a cooling globe in order to con- 

 sider the geometric effects of partial collapse. Because of the fact 

 that with a given mass the body with the greatest surface area is a 

 sphere, and the one with the least surface a four-sided form, it is 

 sometimes argued that our planet is tending towards a tetrahedral 

 earth. In the final analysis, however, it is indicated that the crystal- 

 lographic form could hardly be so simple, but would result in a 

 shape in which each facet of the ground-form consists of a number 

 of smaller facets. The rhombic dodecahedron best fits the figure 

 which the major mountain chains outline on the surface of the 

 globe. ^"^ 



MERIDIANAL DISPOSITION OF THE CONTINENTAL MASSES 



In its basal significance our prevailing notion concerning conti- 

 nental mass is strictly geographic. In its definition tectonics finds 



"Eng. and Mining Jour., Vol. C, p. 466, 1915. 

 "Bull. Geol. Soc. America. Vol. XXTX, p. 76, 1918. 



