Sayles — Dilemma of Paleoclimatolo gists. 159 



seasonally banded Pleistocene clays and the banded 

 Sqnantnm slate. Banded argillites with other tillites 

 in various parts of the world were also noted in this 

 paper. Sederholm 12 and Halle 13 of Sweden expressed 

 their belief in the seasonal nature of certain banded slates 

 in 1913. David and Sussinilch 14 published a paper in 

 1919-20 in which they counted the years by means of 

 banded slate in an upper Carboniferous glacial lake in 

 Australia. At the present time the writer is engaged in 

 a study of banding in various argillites. From the prog- 

 ress so far made, it is difficult to escape the conviction that 

 seasonal deposition existed in many places and periods. 

 That all this banding is of a glacial nature, it is not neces- 

 sary to conclude, for seasonal deposition is going on now 

 far from glaciers. Shaw 15 believes that seasonal deposi- 

 tion is going on at present in the delta of the Mississippi. 

 It will be necessary to compare this banding with the 

 bandings in slates and shales of which there are many 

 examples. Coleman cites the case of the middle member 

 of the Sudbury Series called the McKim Graywacks con- 

 sisting of "thin lavers of interbanded graywacks and 

 slate." 



From a study of a metamorphosed slate, given to the 

 writer by X. E. A. Hinds, which shows regular bandings 

 of coarse and fine materials, it is not impossible to believe 

 that some of the banded schists and possibly some of the 

 regularly banded gneisses were originally seasonally 

 deposited sediments. This is a matter for future investi- 

 gation. 



The Dual Heating System of the Earth. 



With the tremendously long lease of life given to the 

 earth by the discovery of a very much greater number of 

 unconformities and disconformities than we had any idea 

 of a few years ago, as pointed out by Barrell, and Cham- 

 berlin, and the new method of estimating the age of the 

 earth through the study of the transformations of radium, 

 it is evident that during the hundreds of millions of years 

 estimated, there is time for all kinds of climates. In fact, 

 the monotonous, non-zonal arrangement advocated by 

 Manson would not, as noted by Coleman, appear to have 

 been favorable in the least to evolution as it is recorded 

 in the rocks. That there were many more changes of 



