564 



SCIENCE 



[N. S. Vol. XXVIII. No. 721 



According to this theory, then, in pre- 

 Archean times when the crust of the earth 

 had fallen to the temperature at which water 

 would no longer hoil, the water-vapor in the 

 atmosphere began to condense to form the 

 primitive ocean; tidal effects produced ir- 

 regular distribution of crustal tension, caus- 

 ing fractures (most probably along meridian 

 lines), of the solidified crust, thus allowing the 

 seepage of surface-water and the consequent 

 formation of the first volcanic vents. As a 

 result of the constantly increasing weight of 

 a given cone, the supporting crust in the im- 

 mediate vicinity was depressed deeper and 

 deeper below the general level (and still 

 farther depressed through the additional 

 weight of the now water-filled surrounding 

 valley), causing a series of circular wave-like 

 upthrusts separated by water-filled valleys of 

 decreasing depths as the distance from the 

 vent increased. The linear series of vents, 

 along the line of fracture, through continuous 

 growth finally formed a central serrated ridge 

 bounded on each side by a series of parallel 

 ridges of decreasing height. The eastward 

 motion of the atmosphere caused the valleys 

 on the east side to be filled much more rapidly 

 than those on the west side, and thus produced 

 the conditions favorable for the formation of 

 a continental surface sloping to the east, from 

 the volcanic ridge.' 



About Archean times the decreased surface 

 temperature — the changed topography of the 

 rock surface (due to the unequal distribution 

 of the volcanic debris, thus causing differential 

 uplifts), and the consequent partial removal 

 of the cloud envelope in certain regions — 

 made possible the advent of other forms of 

 matter, including living organisms. 



As the thickness of the crust continued to 

 increase — mostly through the addition of ma- 



^ On the area between neighboring fractures ex- 

 tending in an east-west direction more debris was, 

 of course, deposited — forming high table-lands — 

 and the eastward extension of the slope became 

 greater than was the case for fractures extending 

 in a north-south direction. Long-continued local 

 deviation from an eastward motion of the at- 

 mosphere caused a corresponding change in the 

 direction of the local slope. 



terials from the earth's interior — the number 

 of the then existing vents gradually decreased, 

 through the closing of the seepage channels 

 by the volcanic debris. Later on, fresh frac- 

 tures along neighboring lines of least surface 

 strength resulted in the formation of new 

 vents, and a new era of a dust-filled atmos- 

 phere, with its accompanying consequences, 

 was again inaugurated. 



As nearly all the material forming the 

 layers deposited on the primitive crust was 

 taken from the interior of the earth,* the ac- 

 cumulated warping of the crust towards the 

 close of the period during which the sedi- 

 mentary rocks were formed was very great 

 — much greater than could have resulted from 

 shrinkage due to radiation of heat from the 

 inside-Out surface alone! 



If the erupted material for a given rock 

 layer was laid down slowly, through long-con- 

 tinued activity, the evidences of former 

 terrestrial life may be visible throughout the 

 whole thickness of the rock formed; but if 

 the deposition of matter was very rapid, all 

 signs of former life may be wanting, and the 

 total extinction of certain organisms may thus 

 have resulted. 



Some of these layers may have been de- 

 posited in the course of a few years, or even, 

 days, while for the formation of others, cen- 

 turies may have been required. 



With the removal of the lighter constit- 

 uents of the earth's interior to the exterior 

 surface, and the consequent strengthening of 

 the crust, the number of active volcanoes 

 rapidly diminished, thus practically closing 

 the active period of sedimentary rock forma- 

 tion, leaving, in the main, only the ever- 

 present secondary effects, resulting from sur- 

 face erosion, to continue in operation. 



By far the greatest result of these secondary 

 causes is the topographic change produced by 

 the two ice sheets of recent origin; these ice 

 sheets, now mostly confined to the two arctic 

 regions of the earth, but which only a few 



* During the past eighteen years I have pub- 

 lished a number of short papers which favor the 

 theory that the earth's surface is also continually 

 receiving finely divided matter which has been 

 ejected from the sun. 



