﻿548 
  Geological 
  Society. 
  

  

  give 
  any 
  true 
  conception 
  of 
  the 
  scop^ 
  of 
  the 
  present 
  work, 
  which 
  

   covers 
  420 
  quarto 
  pages. 
  That 
  could 
  best 
  be 
  gained 
  by 
  a 
  careful 
  

   perusal 
  of 
  the 
  author's 
  preface. 
  It 
  will 
  suffice 
  to 
  say 
  that 
  

   the 
  author 
  starts 
  from 
  Maxwell's 
  fundamental 
  equations 
  of 
  the 
  

   electromagnetic 
  field, 
  as 
  modified 
  by 
  the 
  introduction 
  of 
  moving 
  

   electrons, 
  deduces 
  general 
  expressions 
  for 
  the 
  electric 
  and 
  magnetic 
  

   forces 
  due 
  to 
  the 
  moving 
  charges, 
  and 
  works 
  out 
  in 
  detail 
  a 
  host 
  

   of 
  problems 
  of 
  vital 
  importance 
  in 
  the 
  present 
  development 
  of 
  the 
  

   theory 
  of 
  electric 
  radiation. 
  Eor 
  example, 
  the 
  last 
  appendix 
  is 
  

   devoted 
  to 
  the 
  Lorentz 
  electron 
  iu 
  regard 
  to 
  its 
  motion 
  in 
  a 
  steady 
  

   electromagnetic 
  field 
  with 
  the 
  electric 
  and 
  magnetic 
  forces 
  

   (1) 
  parallel, 
  (2) 
  perpendicular, 
  (3) 
  inclined 
  at 
  any 
  angle; 
  and 
  

   the 
  final 
  problem 
  is 
  that 
  of 
  the 
  motion 
  of 
  an 
  electron 
  within 
  a 
  

   fixed 
  sphere 
  of 
  uniform 
  electric 
  density. 
  

  

  XLIV. 
  Proceedings 
  of 
  Learned 
  Societies. 
  

  

  GEOLOGICAL 
  SOCIETY. 
  

   [Continued 
  from 
  p. 
  380.] 
  

  

  June 
  11th, 
  1913.— 
  Dr. 
  Aubrey 
  Strahan, 
  F.U.S., 
  President; 
  

   and 
  afterwards 
  W. 
  Whitaker, 
  B.A., 
  F.R.S., 
  E.G.S., 
  in 
  the 
  Chair. 
  

   r 
  l^IIE 
  following 
  communication 
  was 
  read 
  : 
  — 
  

  

  ' 
  On 
  a 
  Group 
  of 
  Metamorphosed 
  Sediments 
  situated 
  between 
  

   Machakos 
  and 
  Lake 
  Magadi 
  in 
  British 
  East 
  Africa.' 
  By 
  John 
  

   Parkinson, 
  M.A., 
  E.G.S. 
  

  

  That 
  part 
  of 
  British 
  East 
  Africa 
  which 
  borders 
  the 
  Athi 
  Plains 
  

   and 
  extends 
  westwards 
  to 
  the 
  eastern 
  edge 
  of 
  the 
  llift 
  Valley, 
  is 
  

   undulating 
  country 
  composed 
  of 
  foliated 
  rocks 
  of 
  ancient 
  appear- 
  

   ance, 
  crossed 
  by 
  pegmatites 
  which 
  are 
  unconnected 
  with 
  any 
  

   apparent 
  granitic 
  intrusions. 
  

  

  A 
  series 
  of 
  crystalline 
  rocks, 
  for 
  which 
  it 
  is 
  proposed 
  to 
  use 
  the 
  

   name 
  Turoka 
  Series, 
  is 
  situated 
  just 
  below 
  the 
  great 
  lava- 
  

   plateau 
  of 
  the 
  Kapiti 
  Plains, 
  and 
  forms 
  the 
  ground 
  drained 
  by 
  the 
  

   head-waters 
  of 
  the 
  Turoka 
  liiver. 
  The 
  following 
  rock-types 
  are 
  

   present 
  in 
  the 
  chief 
  section, 
  in 
  the 
  following 
  apparent 
  upward 
  

   succession 
  : 
  — 
  

  

  (1) 
  Hornblende-schist, 
  seen 
  to 
  a 
  thickness 
  of 
  3 
  feet 
  5 
  inches 
  ; 
  (2) 
  flaggy 
  

   and 
  impure 
  marble, 
  3 
  feet 
  ; 
  (3) 
  biotite-gneiss, 
  2 
  feet; 
  (4) 
  calc-mica-rock 
  

   with 
  lenticles 
  of 
  biotite-gneiss, 
  3 
  feet 
  8 
  inches; 
  (5) 
  hornblende-schist 
  

   similar 
  to 
  No. 
  1, 
  1 
  foot; 
  (6) 
  impure 
  calc-rock, 
  2 
  feet; 
  (7) 
  quartz-felspar- 
  

   vein, 
  2 
  feet 
  ; 
  (8) 
  hornblende-schist, 
  2 
  feet 
  ; 
  and 
  (9) 
  impure 
  calc-rock, 
  

   resembling 
  No. 
  5 
  and 
  about 
  4 
  feet 
  thick. 
  

   A 
  detailed 
  petrographical 
  description 
  is 
  given 
  of 
  the 
  various 
  

   rock-types 
  present 
  in 
  the 
  series 
  which, 
  in 
  addition 
  to 
  those 
  men- 
  

   tioned 
  above, 
  includes 
  kyanite-garnet-gneisses 
  and 
  a 
  scapolite- 
  

   garnet-rock. 
  The 
  author 
  concludes 
  that 
  the 
  group 
  represents 
  a 
  

   series 
  of 
  metamorphosed 
  arenaceous 
  and 
  calcareous 
  sediments, 
  and 
  

   that 
  there 
  is 
  a 
  complete 
  passage 
  from 
  calc-mica-rocks 
  into 
  biotite- 
  

   gneisses. 
  

  

  