﻿Phil. 
  Mag, 
  Ser. 
  6, 
  Vol. 
  18, 
  PI. 
  XXIY. 
  

  

  Fig. 
  II. 
  — 
  Yariatioa 
  of 
  tlie 
  sfcriation 
  for 
  the 
  same 
  spark 
  with 
  

   various 
  powders. 
  

  

  (a) 
  Lycopodi 
  

  

  •76 
  mm. 
  

  

  (5) 
  Pepper 
  "76 
  mm. 
  

  

  (c) 
  Starch 
  •58 
  mm. 
  

  

  (d) 
  Egg-powder 
  -71 
  mm. 
  

  

  (e) 
  Boric 
  Acid 
  '76 
  mm. 
  

  

  The 
  striffi-distances 
  are 
  given 
  along 
  with 
  the 
  name 
  of 
  the 
  powder. 
  

  

  