﻿412 
  Dr. 
  W. 
  Marshall 
  Watts 
  on 
  the 
  Calculation 
  of 
  the 
  

  

  proportional 
  to 
  some 
  power 
  of 
  the 
  atomic 
  weight 
  — 
  though 
  

   nearly 
  true 
  in 
  many 
  families 
  of 
  allied 
  elements, 
  is 
  not 
  strictly 
  

   true 
  in 
  any 
  one 
  case. 
  The 
  diagram, 
  in 
  which 
  the 
  logarithms 
  

   of 
  atomic 
  weights 
  are 
  plotted 
  as 
  ordinates 
  and 
  logarithms 
  of 
  

  

  

  

  

  

  

  Fig.] 
  

  

  .— 
  

  

  Eunge 
  

  

  and 
  Precht's 
  

  

  Law. 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

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  separations 
  as 
  abscissae, 
  shows 
  that 
  the 
  lines 
  joining 
  the 
  points 
  

   in 
  each 
  family 
  of 
  elements 
  are 
  not 
  exactly 
  straight, 
  but 
  are 
  

   slightly 
  curved 
  lines 
  of 
  similar 
  shape, 
  curving 
  downwards 
  at 
  

   the 
  top 
  to 
  pass 
  through 
  the 
  elements 
  of 
  higher 
  atomic 
  weight, 
  

   and 
  curving 
  upwards 
  at 
  the 
  bottom 
  for 
  the 
  elements 
  of 
  small 
  

   atomic 
  w^eight. 
  The 
  lines 
  shown 
  upon 
  the 
  diagram 
  are 
  : 
  — 
  

   (1) 
  0, 
  S, 
  Se; 
  (2) 
  Na, 
  K, 
  Rb, 
  Cs 
  ; 
  (3) 
  Be, 
  Mg, 
  Ca,_Sr, 
  Ba, 
  

   plotted 
  from 
  the 
  differences 
  between 
  the 
  first 
  and 
  third 
  lines 
  

   in 
  the 
  triplet-series 
  ; 
  (4) 
  Mg, 
  Oa, 
  Sr, 
  Ba, 
  and 
  Ra 
  plotted 
  from 
  

   the 
  intervals 
  given 
  in 
  Runge 
  and 
  Pret'lit's 
  paper 
  [Phil. 
  Mag. 
  

   [6] 
  vol. 
  V. 
  p. 
  476 
  (1903) 
  ; 
  Fhys. 
  Zsch. 
  iv. 
  p. 
  285] 
  ; 
  (5) 
  Zn, 
  

   Cd, 
  Hg; 
  (6) 
  B, 
  Al, 
  Ga, 
  In, 
  Tl. 
  

  

  The 
  intervals 
  employed 
  by 
  Runge 
  and 
  Precht 
  are: 
  — 
  

   Mg 
  91-7, 
  Ca 
  223, 
  Sr 
  801, 
  Ba 
  1691, 
  and 
  Ra 
  4858-5. 
  This 
  

   interval 
  occurs 
  three 
  times 
  in 
  the 
  spectrum 
  of 
  radium 
  (4858*3, 
  

   4858'5, 
  and 
  4858*6) 
  ; 
  the 
  interval 
  1691 
  occurs 
  three 
  times 
  

   in 
  the 
  spectrum 
  of 
  barium 
  ; 
  801 
  occurs 
  four 
  times 
  in 
  

   strontium 
  ; 
  223 
  four 
  times 
  in 
  calcium 
  ; 
  and 
  91*7 
  three 
  times 
  

  

  