﻿W. 
  H. 
  Hobhs 
  — 
  Sjpiral 
  Fulgurite 
  from 
  Wisoonsin. 
  17 
  

  

  Art. 
  II.^^ 
  Spiral 
  Fulgurite 
  from 
  Wisconsin; 
  by 
  

   William 
  EL. 
  Hobbs. 
  

  

  There 
  lias 
  recently 
  been 
  presented 
  to 
  the 
  geological 
  collec- 
  

   tion 
  of 
  the 
  University 
  of 
  Wisconsin 
  a 
  lightning 
  tube 
  or 
  

   fnlgurite 
  which 
  has 
  considerable 
  interest 
  because 
  of 
  its 
  shape 
  — 
  

   a 
  perfect 
  dextro-rotary 
  helix. 
  The 
  specimen 
  is 
  the 
  gift 
  of 
  Mr. 
  

   G. 
  H. 
  Kruschke, 
  town 
  clerk 
  of 
  the 
  town 
  of 
  Cutler, 
  Wisconsin, 
  

   who 
  has 
  furnished 
  me 
  with 
  the 
  data 
  for 
  the 
  following 
  descrip- 
  

   tion 
  of 
  the 
  manner 
  of 
  its 
  discovery. 
  

  

  The 
  fulgurite 
  was 
  discovered 
  in 
  October, 
  1897, 
  by 
  Frank 
  de 
  

   Lap, 
  Mr. 
  Kruschke's 
  son-in-law, 
  wliile 
  digging 
  a 
  cellar 
  on 
  the 
  

   southeast 
  quarter 
  of 
  the 
  northeast 
  quarter 
  of 
  Sec. 
  20, 
  T. 
  18, 
  

   E,. 
  2 
  E., 
  Town 
  of 
  Cutler, 
  Juneau 
  County, 
  Wisconsin. 
  It 
  was 
  

   imbedded 
  in 
  a 
  sand 
  knoll 
  about 
  ten 
  feet 
  high, 
  at 
  a 
  distance 
  of 
  

   five 
  feet 
  below 
  the 
  surface. 
  A 
  house 
  has 
  since 
  been 
  built 
  

   upon 
  the 
  spot. 
  

  

  A 
  sample 
  of 
  the 
  sand 
  in 
  which 
  the 
  tube 
  was 
  found 
  has 
  been 
  

   kindly 
  furnished 
  by 
  Mr. 
  Kruschke, 
  and 
  proves 
  on 
  examination 
  

   to 
  be 
  a 
  fairly 
  clean 
  sand, 
  of 
  a 
  light 
  brown 
  color, 
  largely 
  com- 
  

   posed 
  of 
  translucent 
  quartz 
  grains 
  which 
  average 
  about 
  -(^J^th 
  of 
  

   an 
  inch 
  in 
  diameter. 
  The 
  coloring 
  matter 
  appears 
  to 
  be 
  ferric 
  

   oxide. 
  The 
  tube 
  itself 
  is 
  about 
  as 
  thick 
  as 
  a 
  man's 
  thumb, 
  and 
  

   over 
  five 
  inches 
  long. 
  When 
  found 
  it 
  was 
  about 
  three 
  inches 
  

   longer, 
  but 
  Mr. 
  Kruschke 
  reports 
  that 
  a 
  piece 
  was 
  accidentally 
  

   broken 
  off 
  and 
  lost. 
  Examination 
  of 
  the 
  broken 
  end 
  shows 
  

   that 
  the 
  fulgurite 
  is 
  composed 
  of 
  a 
  dull 
  gray 
  si 
  aggy 
  mass, 
  

   filled 
  with 
  larger 
  and 
  smaller 
  cavities 
  exactly 
  like 
  those 
  observed 
  

   in 
  porous 
  natural 
  slags. 
  There 
  are 
  a 
  few 
  dark 
  specks 
  sur- 
  

   rounded 
  by 
  stains 
  of 
  iron 
  oxide. 
  Somewhat 
  excentrically 
  

   located 
  in 
  this 
  end 
  section 
  is 
  a 
  cavity 
  of 
  irregular 
  cross-section 
  

   which 
  appears 
  to 
  extend 
  into 
  the 
  fulgurite 
  as 
  a 
  more 
  or 
  less 
  

   continuous 
  tube, 
  but 
  is 
  so 
  bent 
  and 
  locally 
  contracted 
  that 
  it 
  is 
  

   impossible 
  to 
  follow 
  it 
  for 
  any 
  distance. 
  Its 
  average 
  diameter 
  

   is 
  about 
  3^6-th 
  of 
  an 
  inch, 
  but 
  it 
  is 
  partly 
  filled 
  by 
  blister-like 
  

   eruptions 
  which 
  protrude 
  from 
  its 
  walls. 
  One 
  of 
  these 
  blisters 
  

   which 
  is 
  broken 
  open 
  has 
  walls 
  as 
  thin 
  as 
  paper. 
  

  

  The 
  other 
  end 
  of 
  the 
  fulgurite 
  has 
  not 
  been 
  broken 
  in 
  any 
  

   way 
  but 
  forms 
  four 
  irregular 
  horn-like 
  projections 
  {a-a-a 
  in 
  the 
  

   left 
  of 
  fig. 
  1). 
  The 
  channel 
  (it 
  cannot 
  be 
  asserted 
  that 
  this 
  is 
  

   continuous 
  with 
  the 
  one 
  observed 
  at 
  the 
  other 
  end) 
  emerges 
  at 
  

   one 
  side 
  of 
  the 
  fulgurite 
  {a, 
  in 
  right 
  hand 
  portion 
  of 
  fig. 
  1) 
  

   with 
  only 
  a 
  thin 
  wall 
  less 
  than 
  a 
  millimeter 
  in 
  thickness 
  on 
  the 
  

   outer 
  side. 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Fourth 
  Series, 
  Vol. 
  YIII, 
  No. 
  43.— 
  July, 
  1899. 
  

  

  9 
  

  

  