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  J. 
  M. 
  Blake 
  — 
  Crystal 
  Drawing 
  and 
  Modeling. 
  

  

  The 
  machine 
  contrived 
  to 
  cut 
  these 
  models 
  is 
  simple 
  in 
  prin- 
  

   ciple. 
  The 
  plane 
  positions 
  are 
  taken 
  off 
  the 
  sphere 
  in 
  the 
  same 
  

   manner 
  as 
  when 
  making 
  the 
  gnomonic 
  projection, 
  and 
  the 
  

   machine 
  is 
  set 
  for 
  each 
  plane 
  position 
  before 
  the 
  cat 
  is 
  made. 
  

  

  To 
  cut 
  a 
  model, 
  a 
  block 
  of 
  plaster 
  is 
  cemented 
  on 
  a 
  b;tein 
  

   which 
  screws 
  into 
  a 
  horizontal 
  shaft. 
  The 
  other 
  end 
  of 
  this 
  

   shaft 
  carries 
  a 
  graduated 
  disk 
  and 
  the 
  shaft 
  can 
  be 
  rotated 
  as 
  

   required. 
  This 
  graduated 
  disk 
  corresponds 
  to 
  the 
  equatorial 
  

   ring 
  of 
  the 
  sphere. 
  

  

  There 
  is 
  an 
  iron 
  table 
  with 
  a 
  notch 
  at 
  one 
  side 
  into 
  which 
  

  

  Fig. 
  3. 
  

  

  Fig. 
  3. 
  J. 
  M. 
  Blake's 
  Crystal 
  Modeling 
  Machine. 
  

  

  the 
  block 
  of 
  plaster 
  enters. 
  This 
  table 
  can 
  be 
  rocked 
  in 
  a 
  

   direction 
  at 
  right 
  angles 
  to 
  the 
  shaft, 
  and 
  has 
  a 
  graduated 
  disk 
  

   which 
  reads 
  from 
  zero 
  at 
  each 
  of 
  the 
  two 
  vertical 
  positions 
  of 
  

   the 
  table 
  to 
  90° 
  at 
  the 
  horizontal 
  position, 
  so 
  that 
  one 
  complete 
  

   rotation 
  of 
  the 
  shaft 
  combined 
  with 
  the 
  motion 
  of 
  the 
  table 
  

   through 
  180° 
  covers 
  the 
  position 
  of 
  all 
  possible 
  planes 
  on 
  the 
  

   model. 
  

  

  During 
  the 
  cutting, 
  the 
  saw 
  and 
  file 
  are 
  kept 
  at 
  the 
  proper 
  

   height 
  above 
  the 
  table 
  by 
  attached 
  supports 
  on 
  which 
  they 
  

   glide, 
  and 
  the 
  depth 
  of 
  each 
  cut 
  is 
  determined 
  by 
  adjusting 
  the 
  

   height 
  of 
  the 
  table. 
  The 
  table 
  slides 
  up 
  and 
  down, 
  and 
  has 
  a 
  

   millimeter 
  scale 
  by 
  which 
  the 
  radial 
  distance 
  from 
  the 
  center 
  

   can 
  be 
  measured. 
  

  

  The 
  radii 
  required 
  for 
  proportioning 
  a 
  crystal 
  model 
  can 
  be 
  

  

  