﻿40 
  Becker 
  — 
  Some 
  Queries 
  on 
  Rock 
  Differentiation. 
  

  

  molecular 
  flow. 
  This 
  is 
  demonstrably 
  an 
  excessively 
  slow 
  

   process 
  excepting 
  for 
  distances 
  not 
  exceeding 
  a 
  few 
  centimeters. 
  

   Soret's 
  method 
  of 
  segregation, 
  even 
  if 
  it 
  were 
  not 
  too 
  slow, 
  

   seems 
  inapplicable 
  because 
  it 
  involves 
  a 
  temperature 
  unaccount- 
  

   ably 
  decreasing 
  with 
  depth. 
  The 
  normal 
  variation 
  of 
  tem- 
  

   perature, 
  an 
  increase 
  with 
  distance 
  from 
  the 
  surface, 
  would 
  be 
  

   fatal 
  to 
  such 
  segregation. 
  The 
  least 
  objectionable 
  method 
  of 
  

   segregation 
  would 
  be 
  the 
  separation 
  of 
  a 
  magma 
  into 
  immisci- 
  

   ble 
  fractions 
  ; 
  but 
  this 
  seems 
  to 
  involve 
  a 
  superheated, 
  very 
  

   fluid 
  magma, 
  while 
  the 
  law 
  of 
  fusion 
  and 
  the 
  distribution 
  of 
  

   phenocrysts 
  in 
  rocks 
  indicate 
  that 
  magmas 
  prior 
  to 
  eruption 
  

   are 
  not 
  superheated 
  to 
  any 
  considerable 
  extent 
  and 
  are 
  very 
  

   viscous. 
  

  

  The 
  homogeneity 
  of 
  vast 
  subterranean 
  masses 
  called 
  for 
  by 
  

   the 
  hypothesis 
  of 
  differentiation 
  is 
  unproved 
  and 
  improbable. 
  

   The 
  differences 
  between 
  well-defined 
  rock 
  types 
  are 
  more 
  prob- 
  

   ably 
  due 
  to 
  original 
  and 
  persistent 
  heterogeneity 
  in 
  the 
  compo- 
  

   sition 
  of 
  the 
  globe. 
  Hypogeal 
  fusion 
  and 
  eruption 
  tend 
  rather 
  

   to 
  mingling 
  than 
  to 
  segregation, 
  and 
  transitional 
  rock 
  varieties 
  

   are 
  not 
  improbably 
  mere 
  fortuitous 
  mixtures 
  of 
  the 
  diverse 
  

   primitive, 
  relatively 
  small 
  masses 
  of 
  which 
  the 
  lithoid 
  shell 
  of 
  

   the 
  earth 
  was 
  built 
  up.* 
  

  

  Washington, 
  D. 
  C, 
  October, 
  1896. 
  

  

  *I 
  owe 
  thanks 
  to 
  Dr. 
  Arthur 
  A. 
  Noyes 
  of 
  the 
  Mass. 
  Institute 
  of 
  Technology 
  

   for 
  kindly 
  examining 
  the 
  manuscript 
  of 
  this 
  paper. 
  Dr. 
  Noyes's 
  reputation 
  as 
  an 
  

   investigator 
  in 
  osmotic 
  questions 
  gives 
  his 
  approval 
  of 
  my 
  argument 
  great 
  value. 
  

  

  