proceedings: geological society 195 



from which this material was collected, is composed of brownish to ash- 

 gray silt, sand and gravel, and white marl from a few feet to 100 feet 

 thick. It is generally noncoherent but locally cemented with calcite 

 and forms prominent outcrops, often marked by cross-bedding. The 

 gravel is characterized, like that of the Cypress Hills, by material from 

 the Rocky Mountains. It is found on four extensive plateaus ranging 

 in elevation from 2700 feet, south of Redstone, to 3200 feet in the west 

 side of Boundary Plateau. 



Below the Flaxville level there are extensive areas, varying in eleva- 

 tion from 2500 to 2700 feet, in which the bedrock is generally near the 

 surface. Several exposures of quartzite gravel interstratified with yel- 

 lowish silt lie at an elevation of 2500 feet a few miles north of Milk 

 River. A single fossil tooth collected from the gravel was submitted 

 to Dr. Gidley, who pronounces it either a recent or Pleistocene horse. 

 The erosion of these large areas is thought to have been accomplished 

 in early Pleistocene time. Since early Pleistocene the streams have 

 eroded their valleys, but this erosion was clearly before the last great 

 glacial advance, and the valley floors are therefore regarded as having 

 been formed during late Pleistocene and Recent times. 



Discussion: W. C. Alden said the gravels are well rounded, and that 

 erosion to a depth of at last 1000 feet occurred between the time of an 

 older glaciation and the Wisconsin. J. W. Gidley suggested that the 

 fossils in the gravels were derived from older formations. 



J. C. Hostetter: The linear force of growing crystals. The literature 

 on this subject shows that a loaded crystal will grow against a load and 

 lift it. This was first demonstrated by Becker and Day in 1905 and, 

 although their conclusions were attacked by Bruhns and Mecklenburg in 

 1913, the recent papers of Taber and of Becker and Day show definitely 

 that the linear force exerted by growing crystals may develop large pres- 

 sures and hence must be considered a factor in vein formation. In 

 these latter papers the explanation given for Bruhns and Mecklenburg's 

 failure to observe an elevation of a load placed on a crystal when an 

 unloaded crystal was growing in the same solution was that the solu- 

 bility of the loaded crystal was greatly increased by the pressure acting 

 on it, and therefore the degree of supersaturation sufficient for the 

 growth of the unloaded crystal was insufficient to cause growth of the 

 loaded crystal. 



We should here distinguish between pressure acting equally on both 

 phases of a system — uniform pressure — and pressure which acts in ex- 

 cess on the solid — non-uniform pressure. The effects are quite differ- 

 ent in the two cases, as has been pointed out by Johnston and Adams. 

 The change in solubility produced by uniform pressure is very small as 

 compared to the effect of temperature — 1000 atmospheres so applied 

 being equivalent to about 14°. Preliminary experiments on the effect of 

 non-uniform pressure on solubility under carefully controlled condi- 

 tions indicate that the effect of pressure acting on the solid but not on 

 the liquid is much smaller than that brought about by the same pressure 

 acting uniformly on solid and liquid. 



