﻿18 
  W. 
  II. 
  IloUbs 
  — 
  Spiral 
  Fulgurite 
  from 
  Wisconsin. 
  

  

  The 
  surface 
  of 
  the 
  fulgurite 
  is 
  very 
  irregular, 
  being 
  traversed 
  

   by 
  corrugations 
  whose 
  greatest 
  extension 
  is 
  in 
  the 
  direction 
  of 
  

   the 
  longer 
  axis 
  of 
  the 
  fulgurite, 
  though 
  they 
  exhibit 
  some 
  

   tendency 
  to 
  wrap 
  themselves 
  around 
  it 
  in 
  a 
  dextro-rotary 
  man- 
  

   ner. 
  These 
  corrugations 
  appear 
  to 
  be, 
  for 
  the 
  most 
  part, 
  thin- 
  

   walled 
  tubes 
  (J, 
  at 
  the 
  left 
  in 
  fig. 
  1) 
  which 
  are 
  not 
  now 
  con- 
  

  

  ■ 
  Fig. 
  1. 
  Spiral 
  fulgurite 
  from 
  Culler, 
  Wisconsin, 
  showing 
  opposite 
  sides. 
  The 
  

   units 
  in 
  the 
  scale 
  are 
  inches, 
  a, 
  a, 
  a, 
  in 
  the 
  figure 
  at 
  the 
  left, 
  horn-like 
  protuber- 
  

   ances 
  terminating 
  the 
  fulgurite, 
  h 
  of 
  the 
  same 
  portion 
  of 
  the 
  figure, 
  corruga- 
  

   tions 
  broken 
  open 
  and 
  exhibiting 
  thin-wallcd 
  tubes, 
  a 
  in 
  figure 
  at 
  the 
  right, 
  

   point 
  of 
  emergence 
  of 
  main 
  channel 
  (hidden 
  in 
  the 
  view). 
  

  

  tinuous 
  passages, 
  but 
  are 
  so 
  distorted 
  and 
  contracted 
  locally 
  as 
  

   to 
  suggest 
  that 
  they 
  have 
  suffered 
  collapse 
  since 
  their 
  forma- 
  

   tion. 
  

  

  Over 
  the 
  entire 
  outer 
  surface 
  of 
  the 
  fulgurite 
  are 
  grains 
  of 
  

   sand 
  which 
  show 
  varying 
  degrees 
  of 
  former 
  fusion. 
  Those 
  

   which 
  have 
  been 
  completely 
  fused 
  are 
  opaque 
  and 
  M'hite, 
  and 
  

   are 
  firmly 
  cemented 
  to 
  the 
  glass 
  of 
  the 
  tube. 
  The 
  others 
  

   adhere 
  less 
  firmly 
  and 
  where 
  distributed 
  abundantly 
  appear 
  

   brown, 
  as 
  in 
  the 
  sample 
  of 
  loose 
  sand 
  from 
  the 
  locality. 
  The 
  

   photographs 
  shown 
  in 
  fig. 
  1 
  exhibit 
  opposite 
  sides 
  of 
  the 
  fulgu- 
  

   rite 
  and 
  indicate, 
  as 
  well 
  as 
  any 
  photographs 
  are 
  likely 
  to 
  do, 
  

   its 
  perfectly 
  helical 
  form. 
  The 
  only 
  fulgurite 
  known 
  to 
  me 
  

  

  