Mat 13, 1910J 



SCIENCE 



759 



auite -with which the quartz is intimately inter- 

 grown. The contrast between the low tempera- 

 ture here indicated and the temperature at which 

 graphite is produced in the electric furnace (cer- 

 tainly over 2000° C.) emphasizes the importance 

 of the presence of other substances and possibly 

 01 the time element in crystallization under nat- 

 ural conditions. Mr. T. Wayland Vaughan an- 

 nounced the existence of two Miocene horizons at 

 Porter's Landing, Ga., the upper one of which is 

 definitely correlated with the Duplin Marl of 

 North Carolina and the lower one of which is the 

 approximate equivalent of the Calvert formation 

 of Maryland. 



Regular Program 

 Weathering of Coal in the Arid Region of the 

 Oreen River Basin, Sweetwater County, Wy- 

 oming: At.fbed R. Schultz. 

 Coal beds in arid as well as in moist climates 

 show considerable deterioration along the outcrop 

 and this deterioration in many places extends to 

 the base of the belt of weathering or well down 

 into it. The belt of weathering, from a geologist's 

 point of view, is the surficial belt extending from 

 the surface of the earth to the level of ground 

 water. In this belt all the important reactions 

 characteristic of the zone of katamorphism, 

 namely, oxidation, carbonation, hydration and 

 solution, exert their maximum activity. The 

 zone of katamorphism is the zone in which altera- 

 tions of rocks result in the production of simple 

 compounds from more complex ones. This zone 

 extends from the surface of the earth to a depth 

 of 10,000 meters and is divisible into two belts: 

 (1) an upper belt of weathering and (2) a lower 

 belt of cementation, the two being delimited by 

 the level of ground water. As the ground-water 

 level in arid regions lies at considerably greater 

 depths below the surface than in well-watered 

 regions, it is but natural to suppose that the belt 

 of weathering extends to proportionately greater 

 depths in dry than in moist climates. It would 

 then follow that the deterioration of coal should 

 extend farther below the surface in arid regions 

 than in regions where the top of the water table 

 lies only a few feet below the surface of the 

 ground. That the deterioration of the coal does 

 not always extend to the bottom of the belt of 

 weathering as above defined or even to a consid- 

 erable depth into this belt is a fact not well 

 known. In order to ascertain to what extent and 

 depth the coal beds in the arid regions have been 

 altered a total of 85 samples were collected and 

 analyzed from the coal beds in the Rock Springs 



held. Of these 45 were collected from coal beds 

 in the Rock Springs group, 20 from coal beds in 

 tne Almond group, 10 from coal beds in the Black 

 Buttes group, and 10 from coal beds in the Black 

 Rock group. The first two are of Montana age, 

 the third " Laramie," and the fourth Tertiary. 



Considered with regard to physical as well as 

 chemical properties the coals occurring in these 

 four groups fall into two classes, bituminous and 

 subbituminous. The bituminous class includes all 

 the high-grade coal of the Rock Springs group; 

 the subbituminous class all the coal of the 

 Almond, Black Buttes and Black Rock groups. 

 The difi^erence between these two classes is phys- 

 ical as well as chemical. The Rock Springs coal 

 usually has a lower percentage of water, remains 

 firm and compact on exposure to air, and stands 

 shipping well without breaking down. The coals 

 from the three overlying groups, although from 

 different horizons and of different ages, have 

 essentially the same physical properties and bear 

 a regional resemblance to one another. On ex- 

 posure to the sun and open air they alter very 

 rapidly, lose their bright luster, air slack and 

 break down into irregular blocks or powder. 

 Cracks usually form along the bedding planes and 

 somewhat irregularly in other directions. The 

 coal does not stand shipping without breaking 

 down or slacking, unless it is kept from the sun 

 and circulating air while in transit. It is prob- 

 able that the Rock Springs coal has undergone a 

 more complete devolatilization, deoxygenation and 

 concentration and does not assimilate oxygen so 

 rapidly on exposure to the air as the other coals. 

 The hydrocarbon compounds represented by the 

 Rock Springs coal appear to be much more stable 

 under atmospheric conditions than those repre- 

 sented by the higher coals. It is clearly evident 

 that along the outcrop of a coal bed and down 

 tne dip at least three zones may be rec(^nized — 

 tkose of surface weathering, under-ground weath- 

 ering and unaltered coal. 



The results obtained in the Rock Springs field 

 indicate that so far as coal decomposition or 

 deterioration is concerned the belt of weathering 

 in arid regions may be divided into two members. 

 Coal in the lower member of the belt apparently 

 shows no greater efi'ect of weathering than the 

 coal below the level of groimd water, but coal in 

 the upper member, or in the surficial belt of 

 weathering, shows remarkable deterioration and 

 decomposition. The protection of the coal above 

 the level of ground water in the lower member of 

 the belt of weathering may in part be accounted 



