WRIGHT AND HOSTETTER! CRYSTAL GROWTH 405 



oi the accumulation of gas under an impervious crust, the re- 

 lease being continuous at times of rapid circulation and spas- 

 modic during stagnant times. 



The zone of bottom heat reaches a maximum not greater than 

 that of the fount aining grottoes, and the gradient must recurve to 

 lower temperatures in the stiff bench magma below. Continued 

 measurement will show whether the relatively even temperature 

 (1120°-1170°) of the lower 5 meters of the lake is that of the 

 rising conduit lava. The writer surmises that it is hotter than 

 the conduit lava, because the latter generally crusts over ex- 

 tensively and shows low incandescence. Geologic evidence 

 from raised portions of the under-lake marginal slopes indicates 

 that foundered crusts pile up beneath the lake, and experiment 

 shows that they would glaze over and confine air. On reaching 

 the bottom of the lava pool such accumulations, by gradually 

 releasing air to react with the volcanic gas, would produce 

 reheating. They would continuously soften and disintegrate, 

 but during the prolonged reaction, always supplied by new 

 foundering, the bottom would present what the measurement 

 appears to reveal, a combination of viscosity and high tempera- 

 ture. The gaseous products of the reaction would accumulate 

 in the zone of cooling and would be released explosively as cen- 

 tral or border fountains where the accumulation became ex- 

 cessive. As yet it has not been possible to force a pipe down 

 into the stiffer and lower bottom material which might show 

 declining temperature. At the best, exploration of the deep 

 region is difficult and somewhat dangerous, and such experi- 

 ments as the immersion of May 2 must be carefully prepared; 

 with expectation of many reverses. 



CRYSTALLOGRAPHY. — The thermodynamic reversibility of the 

 equilibrium relations between a strained solid and its liquid^ 

 F. E. Wright and J. C. Hostetter, Geophysical Laboratory, 



In the thermodynamical treatment of the effect of pressure 

 on the melting temperature or on the solubility of a crystal it 

 has been customary tacitly to assume that the process is rever- 

 sible, because only under such conditions do the equilibria rela- 



