760 



SCIENCE 



[N. S. Vol. XXXI. No. 802 



for by the accompanying beds of clay and shale, 

 which tend to shut out the oxygen and free cir- 

 culation almost as readily as the ground water. 

 The analyses show that the proportions of the 

 various constituents are about the same whether 

 the sample of coal was taken near the surface or 

 at a greater depth, the only exception being in the 

 oxygen, which in every case is perceptibly higher 

 near the surface than at greater depths and by 

 its excess shows the extent of the surficial belt 

 of weathering. The ash, sulphur and hydrogen 

 content remain fairly constant. There appears 

 to be a slight increase in the amount of hydrogen 

 and ash in the samples obtained near the surface, 

 with a corresponding decrease in the amount of 

 sulphur. It appears from this that the belt of 

 surficial weathering is one of marked oxidation 

 and in this field for the most part lies near the 

 surface, in few places, if anywhere, extending to 

 the ground-water level. If the coal is not open or 

 exposed to the air the weathered zone does not, as 

 a rule, extend more than 150 feet down the dip 

 of the beds, or 50 feet below the surface. Along 

 slopes and mine or prospect entries the coal 

 weathers back several hundred feet from the 

 mouth of the mine and several hundred feet below 

 the surface. It is known that in one old mine the 

 coal has changed at least 20 feet back from the 

 face of an old entry approximately 227 feet down 

 in the mine and that deterioration extends back 

 into the mine 573 feet from its mouth. It is very 

 probable that in an abandoned mine remaining 

 open to the air oxygenation in time extends 

 throughout the mine and that the coals of lower 

 grade show the effect of oxygenation much more 

 than the high-grade coals. 



Evidences of Paleobotany as to Geological Cli- 

 mate: David White and F. H. KpfowLTON. 

 On the climatological criteria offered by the 

 fossil floras, their characters, distribution and 

 changes, the authors base the following tentative 

 conclusions as to general conditions and prin- 

 ciples : 



1. Relative uniformity, mildness (probably sub- 

 tropical in degree) and comparative equability 

 of climate, accompanied by a high humidity, have 

 prevailed over the greater part of the earth, 

 extending to, or into, the polar circles, during the 

 greater part of geologic time since, at latest, the 

 Middle Paleozoic. This is the regular, the ordi- 

 nary, the normal condition. From a broad point 

 of view these conditions are relatively stable. 



2. The development of strongly marked climatic 

 zones, at least between the polar circles, is excep- 



tional and abnormal. It is usually confined to 

 short intervals, or to intermittently oscillating 

 short intervals, all within relatively short periods. 



3. The periods of abnormal climatic differentia- 

 tion are characterized by the development of 

 extremes — i. e., by extreme and abnormal heat 

 or cold (glaciation), humidity or aridity — which 

 are local or regional in their occurrence and 

 variable or unstable. 



4. The brief geological period in which we live 

 is a part of one of the most strongly developed 

 and unstable of these abnormal intervals of radical 

 change. The assumption that climatic variations, 

 contrasting extremes and complexity of combina- 

 tion and geographic distribution of climatic fac- 

 tors, such as now exist, are normal or essential, 

 and that they were present also, though in 

 slightly less degree, in all geological periods 

 appears to be without paleobotanical warrant. 

 The proposition that we are still in the glacial 

 epoch is paleontologically true. We have no evi- 

 dence that in any other post-Silurian period, with 

 perhaps the exception of the Permo-Carboniferous 

 glacial period, have the climatic distribution and 

 segregation of life been so highly differentiated 

 and complicated as in post-Tertiary time. 



5. The distribution and characters of most of 

 the great pre-Tertiary floras show that time and 

 again during the great periods of relative uni- 

 formity and equable mildness, plant associations 

 were able to pass from one high latitude to the 

 opposite without meeting an efiicient climatic 

 obstruction in the equatorial region. The un- 

 changed features of the species and the grouping 

 of the latter show that the climatic elements of 

 the environment must have been similar through- 

 out the range of the flora. Therefore it appears 

 that a climate essentially the same must have 

 continued from one latitude to the other without 

 the interposition at those periods of a torrid 

 equatorial zone. The absence of the latter may 

 also be inferred from the relative uniformity of 

 distribution in other directions, as shown by the 

 remarkable east-west and radial ranges of the 

 floras. 



6. The development and existence of torridity— 

 i. e., of a torrid zone in the equatorial belt or any 

 other great region of the earth— is concomitant 

 and causally connected with the development of 

 regional frost. It would appear that the occur- 

 rence of a torrid zone is peculiar to abnormal or 

 glacial intervals. 



Edsoit S. Bastin, 

 Secretary 



