﻿*2-2± 
  Samuel 
  Wendell 
  Williston. 
  

  

  following 
  scheme 
  differs 
  only 
  in 
  minor 
  details 
  from 
  the 
  

   more 
  conservative 
  of 
  the 
  generally 
  accepted 
  views, 
  and 
  

   those 
  differences 
  are, 
  for 
  the 
  most 
  part, 
  the 
  writer's 
  own 
  

   opinions, 
  to 
  be 
  taken 
  for 
  what 
  they 
  are 
  worth. 
  It 
  may 
  be 
  

   said 
  decisively 
  that 
  no 
  classification 
  of 
  the 
  reptiles 
  into 
  

   major 
  groups, 
  into 
  superfamilies 
  or 
  subclasses, 
  that 
  has 
  

   so 
  far 
  been 
  proposed 
  is 
  worthy 
  of 
  acceptance. 
  . 
  . 
  . 
  

   And 
  we 
  have 
  very 
  much 
  more 
  to 
  learn 
  about 
  the 
  early 
  

   reptiles 
  before 
  any 
  general 
  classification 
  of 
  the 
  reptiles 
  

   can 
  be 
  securely 
  founded. 
  ' 
  ' 
  It 
  was 
  hoped 
  that 
  Williston 
  's 
  

   projected 
  book 
  on 
  the 
  Evolution 
  of 
  the 
  Reptiles 
  would 
  

   give 
  further 
  expression 
  to 
  his 
  taxonomic 
  views. 
  The 
  

   importance 
  of 
  publishing 
  this 
  work, 
  even 
  though 
  incom- 
  

   plete, 
  is 
  very 
  great. 
  

  

  I 
  have 
  before 
  me 
  many 
  letters 
  from 
  Williston 
  's 
  pupils 
  

   and 
  colleagues, 
  written 
  in 
  response 
  to 
  certain 
  inquiries 
  of 
  

   mine. 
  They 
  are 
  unanimous 
  in 
  their 
  expression 
  of 
  the 
  

   highest 
  esteem 
  for 
  the 
  man, 
  the 
  teacher 
  and 
  the 
  investi- 
  

   gator, 
  the 
  soundness 
  of 
  whose 
  observations 
  and 
  conclu- 
  

   sions 
  will 
  grow 
  more 
  and 
  more 
  apparent 
  with 
  the 
  passing 
  

   of 
  time. 
  

  

  Richard 
  Swann 
  Lull. 
  

  

  SCIENTIFIC 
  INTELLIGENCE. 
  

  

  Chemistry 
  and 
  Physics. 
  

  

  1. 
  Properties 
  of 
  Lead 
  Isotopes. 
  — 
  Theodore 
  W. 
  Richards, 
  

   who 
  has 
  previously 
  made 
  important 
  investigations 
  in 
  regard 
  to 
  

   the 
  differences 
  between 
  ordinary 
  lead 
  and 
  the 
  lead 
  from 
  radio- 
  

   active 
  minerals, 
  has 
  recently 
  in 
  cooperation 
  with 
  Walter 
  C. 
  

   Schumb 
  determined 
  the 
  refractive 
  index 
  and 
  solubilities 
  of 
  com- 
  

   mon 
  lead 
  nitrate 
  and 
  of 
  "uraniolead" 
  nitrate 
  from 
  Australian 
  

   material. 
  The 
  highly 
  interesting 
  fact 
  is 
  revealed 
  that 
  while 
  the 
  

   atomic 
  weights 
  of 
  the 
  two 
  kinds 
  of 
  lead 
  are 
  207.20 
  and 
  206.41, 
  

   and 
  while 
  the 
  densities 
  of 
  the 
  metals 
  vary 
  in 
  the 
  same 
  ratio, 
  

   there 
  is 
  no 
  appreciable 
  difference 
  in 
  the 
  refractive 
  indices 
  of 
  the 
  

   solid 
  nitrates, 
  as 
  they 
  were 
  found 
  as 
  a 
  mean 
  of 
  many 
  concordant 
  

   determinations 
  at 
  20° 
  to 
  be 
  1.7815 
  and 
  1.7814. 
  On 
  the 
  other 
  

   hand, 
  the 
  solubilities 
  of 
  the 
  salts 
  at 
  25.02° 
  were 
  found 
  to 
  vary, 
  

   being 
  37.342 
  and 
  37.280 
  parts 
  in 
  100 
  parts 
  of 
  water, 
  but 
  these 
  

   results 
  are 
  precisely 
  proportional 
  to 
  the 
  molecular 
  weights 
  of 
  

   the 
  salts, 
  within 
  the 
  limits 
  of 
  experimental 
  error, 
  so 
  that 
  the 
  

   molal 
  solubilities 
  in 
  1000 
  parts 
  of 
  water 
  are 
  practically 
  identical, 
  

  

  