80 proceedings: geological society 



about by pressure may account for the solidification of crystals com- 

 pressed in contact with their solution by loosely fitting pistons — as found 

 by James Thomson, Le Chatelier, and Spring — without the necessity 

 of postulating large increases in solubility due to pressure. 



In preliminary experiments, individual crystals were subjected to 

 stress at constant temperature by direct loading, and the effect on the 

 concentration of the surrounding solution studied, by measuring the 

 conductivity. No change in concentration was found. The test was 

 sufficiently sensitive to show that the effect of non -uniform pressure is 

 much less than that produced by the same pressure acting uniformly, 

 and not many times greater, as had been postulated by Johnston and 

 Adams. 



However, in another series of experiments in which an unloaded 

 crystal was placed alongside a loaded crystal, the former grew at the 

 expense of the latter, showing that a very slight increase of solubility 

 was produced by the stress. The method of loading the crystals has 

 a large influence on the effects found, thus indicating the importance 

 of the stress distribution. 



In conclusion, the experiments of Becker and Day on the linear force 

 of growing crystals were cited as indicating the stability of a crystal in 

 its solution, even when subjected to pressure. In their experiments 

 loaded crystals were found to lift the load during growth, although 

 the pressures on the supporting edges of the crystals were finally of the 

 order of magnitude of the crushing strength of the crystal. 



Discussion. The three papers were discussed by Messrs. Briggs, 

 Buckingham, Hostetter, Sosman, and Williamson. Mr. Hostetter 

 remarked that the reason for the effect of hydrostatic pressure on melt- 

 ing and solubility was much more obvious than that for the similar 

 effect due to strain in the solid only, as hydrostatic pressure directly 

 aids or opposes the volume changes accompanying such change in state. 

 Mr. Buckingham referred to the complications introduced by the 

 change in cross section of a crystal under load as it dissolves. 



Correction. In the minutes of the 780th meeting, this Journal, 

 7 : 24. 1917, for " Messrs. Ferner and Rothermel were appointed tellers," 

 read, "Messrs. Fenner and Rothermel were appointed tellers." 



D. H. Sweet, Secretary. 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



The 311th meeting was held in the lecture room of the Cosmos Club 

 on November 22, 1916. 



INFORMAL COMMUNICATION 



T. W. Stanton : A Cretaceous volcanic ash bed on the Great Plains in 

 North Dakota. Near Linton, North Dakota, in the southern part of 

 the State about 15 miles east of the Missouri River, there are several 

 conspicuous white outcrops that at a distance suggest chalk or diato- 

 maceous earth. At one of the best exposures, 1 mile southeast of Lin- 



