484 proceedings: geological society 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



The 295th meeting was held in the lecture room of the Cosmos Club 

 on April 14, 1915. 



INFORMAL COMMUNICATIONS 



E. W. Shaw : Sulphur in rocks and in river waters. Sulphur is indi- 

 cated by analyses to be about 36 times as abundant in rivers as in rocks 

 and yet the mineral matter of rivers must come directly or indirectly 

 from the rocks. Several questions arise. Is the sulphur being brought 

 back from the sea to the land so that it makes two or more trips while 

 other elements make one? Evidently not. Are there other agents 

 which carry loads in which sulphur is scant or wanting? The dust 

 carried by the wind probably contains very little sulphur, but the 

 quantity reaching the sea is small compared with the rock waste car- 

 ried by streams. The clay, silt, sand, and gravel carried by streams 

 contain, no doubt, less sulphur than the rocks do, and assist consider- 

 ably in explaining the discrepancy, but it is known that the amount 

 of material carried in suspension by streams is not more than about 

 twice that carried in solution, and hence if the suspended matter con- 

 tains no sulphur at all the discrepancy would still be about 1200 per 

 cent. The bottom load of streams is an unknown quantity, but it is 

 probably considerably less than the suspended load. Is sulphur more 

 abundant in rivers because sulphur compounds are in general more 

 soluble than others? The long periods of geologic time and great 

 amount of erosion which the lands as a whole have suffered would seem 

 to nullify this possibility, for in the lowering of a land surface hundreds 

 or thousands of feet, both soluble and insoluble materials, must be 

 removed. But the removal may not proceed at a uniform rate and 

 hence arises the question as to whether or not present conditions are 

 unusual. Apparently they are, first, because of the activities of man 

 in bringing sulphur-containing minerals — pyrite, gypsum, etc. — within 

 reach of streams; and second, because of a generally lower position of 

 ground water surface and thicker zone of active oxidation at present 

 due to the unusual height of the continents and to the withdrawal of 

 water from wells. Coal mining alone is apparently responsible for a 

 considerable part of the discrepancy, especially since most of the waters 

 analyzed come from well settled regions. However, a part of the sul- 

 phur sent into the atmosphere is carried out over the ocean and there 

 brought down by rain. Finally, it appears that the amount of sulphur 

 in the earth's crust has been underestimated because, first, the speci- 

 mens of sedimentary rocks analyzed were taken from at or near the 

 surface where much of the sulphur has been leached out and carried 

 away, and second, because sedimentary rocks are weighted at only 5 

 per cent, whereas most of the waters have access only to such rocks. 

 The moral is that composite samples of strata lying below the surface 

 of ground water should be made up and analyzed. 



