﻿in 
  Their 
  Thermodynamic 
  Relations. 
  

  

  175 
  

  

  200 
  meters 
  below 
  the 
  surface 
  of 
  the 
  ocean. 
  Otherwise 
  the 
  

   water 
  would 
  be 
  vaporized 
  and 
  inactive. 
  This 
  depth 
  is 
  marked 
  

   del 
  in 
  the 
  diagram 
  to 
  show 
  its 
  relation 
  to 
  the 
  surrounding 
  ocean 
  

   and 
  shore 
  lines. 
  

  

  I>, 
  in 
  the 
  diagram, 
  represents 
  the 
  adjoining 
  land, 
  with 
  the 
  

   isotherms 
  higher 
  than 
  200° 
  located 
  in 
  place. 
  The 
  newest 
  

   measurements 
  put 
  these 
  about 
  400 
  kilometers 
  apart 
  per 
  100° 
  

  

  20- 
  

  

  C. 
  If 
  therefore 
  water 
  from 
  anywhere 
  below 
  the 
  level 
  dd 
  

   enters 
  the 
  rock 
  by 
  whatever 
  catastrophe, 
  penetrating 
  as 
  far 
  as 
  

   the 
  isotherm 
  for 
  200°, 
  the 
  rock 
  there, 
  if 
  of 
  the 
  character 
  of 
  the 
  

   above 
  experiments, 
  will 
  become 
  liquified, 
  apart 
  from 
  pressure. 
  

   The 
  hydrated 
  silicate 
  in 
  place 
  is 
  thus 
  virtually 
  fluid 
  below 
  the 
  

   contours 
  of 
  the 
  isotherm 
  8 
  kilometers 
  below 
  the 
  surface. 
  Thus 
  

   the 
  depth 
  of 
  the 
  isotherm 
  of 
  potential 
  fusion 
  is 
  placed 
  about 
  five 
  

   times 
  as 
  near 
  the 
  surface 
  as 
  would 
  be 
  the 
  case 
  for 
  the 
  corre- 
  

   sponding 
  igneous 
  fusion. 
  Estimating 
  the 
  pressure 
  on 
  the 
  210° 
  

   isotherm 
  as 
  much 
  below 
  3000 
  atmospheres, 
  the 
  whole 
  pheno- 
  

   menon 
  is 
  in 
  an 
  interesting 
  way 
  placed 
  within 
  laboratory 
  reach. 
  

  

  Brown 
  University. 
  Providence, 
  R. 
  I. 
  

  

  