824 J. BAERELL MEASUREMENTS OF GEOLOGIC TIME 



The lack of notice given to his paper seems to have been due to a lack 

 of that conclusive demonstration which is needed to force attention to a 

 vievi^ not in accord with the times. 



ESTIMATES OF TIME BASED ON RHYTHMS IN SEDIMENTATION 



Through all of earth history the existence of a solid crust requires 

 that, no matter how effective as a heat retainer is the atmosphere, the 

 maintenance of the atmospheric and hydrospheric envelope in gaseous 

 and fluid form has been due to solar energy, and not in any appreciable 

 degree to heat derived from the earth. The solar heat is now and always 

 must have been delivered in largest quantity to the equatorial zone and 

 in small amount to the polar regions, yet the circulation systems are so 

 efficient that even in this age of polar ice the temperature of the polar 

 night falls only a little way comparatively toward absolute zero. The 

 circulation system which spreads out the heat is kept in motion by the 

 loss of heat in higher latitudes and the latitu'dinal difference in tempera- 

 ture which results. During most of geologic time the efficiency of the 

 circulation system was so high that relatively small differences of tem- 

 perature sufficed to maintain it. 



But the spread of solar energy by means of the circulation systems 

 from low to high latitudes and from seas to inland regions must always 

 have been rhythmic. This is a very general condition, where speed of 

 flow is limited by the resistances which are set up. In the irregularities 

 of motion the flow seeks that direction where the resistances are tem- 

 porarily lessened; increasing in speed, the resistances are increased until 

 they in turn overcome the inertia of the motion. As a result, a cyclic 

 damping of the flow is produced in the one place or time with a corre- 

 sponding acceleration in another. Thus the' flow of energy proceeds in 

 pu:lses. The icyclonic storms of the temperate zones and the blizzards of 

 the polar ice-caps illustrate short-term rhythms of this nature. The 

 shifting of storm tracks and runs of similar weather may represent oscil- 

 lations in equilibrium of longer term due to such terrestrial conditions. 

 Such pulses may be classified as terrestrial climatic rhythms. 



But similar laws of oscillation control the liberation of energy from 

 the sun. To maintain its surface temperature, convective movements 

 must stir its mass, actuated by loss of energy, manifested by cooling and 

 condensation at the surface, renewed by the transformation of other modes 

 of energ}'- into thermal form at depth. 



To begin with short-term rhythms and passing to those of longer term, 

 a rhythm has been detected in the change in the frequency of solar prom- 

 iiionoos in a period of about three years. 



