﻿122 
  Transactions. 
  — 
  Miscellaneous. 
  

  

  The 
  Sim, 
  by 
  attractiBg 
  a 
  body 
  from 
  infinite 
  space, 
  would 
  give 
  it 
  a 
  velocity 
  

   of 
  378 
  miles 
  a 
  second, 
  or 
  each 
  unit 
  of 
  mass 
  would 
  develope 
  about 
  forty 
  

   million 
  units 
  of 
  heat. 
  If 
  we 
  suppose 
  two 
  bodies, 
  each 
  half 
  the 
  size 
  of 
  the 
  

   sun, 
  to 
  come 
  together 
  by 
  mutual 
  attraction 
  alone, 
  then 
  each 
  unit 
  of 
  mass 
  

   would 
  develope 
  about 
  twenty 
  million 
  units 
  of 
  heat. 
  If, 
  on 
  the 
  other 
  hand, 
  

   two 
  bodies 
  twice 
  the 
  mass 
  of 
  the 
  sun 
  come 
  together, 
  each 
  unit 
  of 
  mass 
  

   would 
  have 
  four 
  times 
  the 
  force 
  acting 
  upon 
  it 
  through 
  equal 
  spaces, 
  and 
  

   each 
  unit 
  of 
  mass 
  would 
  conseqitently 
  develope 
  four 
  times 
  as 
  much 
  heat. 
  

   If 
  the 
  impact 
  of 
  such 
  bodies 
  were 
  imperfect, 
  as 
  we 
  have 
  seen 
  the 
  general 
  

   case 
  would 
  be, 
  a 
  piece 
  of 
  each 
  would 
  be 
  cut 
  off, 
  and 
  these 
  two 
  pieces 
  would 
  

   coalesce. 
  Suppose 
  a 
  quarter 
  of 
  each 
  be 
  struck 
  off, 
  a 
  body 
  of 
  the 
  mass 
  of 
  

   the 
  sun 
  would 
  be 
  joi'oduced, 
  but 
  it 
  would 
  have 
  four 
  times 
  the 
  temperature 
  

   the 
  sun 
  would 
  have, 
  assuming 
  the 
  sun 
  to 
  have 
  been 
  formed 
  by 
  direct 
  impact 
  

   and 
  complete 
  coalescence. 
  Each 
  unit 
  of 
  mass 
  in 
  this 
  case 
  would 
  have 
  

   approximately 
  eighty 
  million 
  units 
  of 
  heat 
  ; 
  and 
  the 
  temperature 
  will 
  depend 
  

   upon 
  the 
  specific 
  heat 
  of 
  the 
  material, 
  and 
  may 
  be 
  much 
  higher 
  than 
  this. 
  

   I 
  will 
  now 
  show, 
  in 
  the 
  case 
  of 
  partial 
  collision, 
  how 
  small 
  relatively 
  the 
  

   work 
  of 
  cutting 
  off 
  the 
  piece 
  is 
  compared 
  to 
  the 
  energy 
  available. 
  It 
  

   appears 
  to 
  me 
  that 
  in 
  all 
  cases 
  the 
  energy 
  needed 
  for 
  shearing 
  force 
  has 
  its 
  

   superior 
  limit 
  in 
  the 
  latent 
  heat 
  of 
  fusion. 
  This, 
  in 
  the 
  case 
  of 
  ice, 
  is 
  about 
  

   one-fiftieth 
  that 
  of 
  combustion, 
  and 
  combustion 
  is 
  about 
  one 
  twenty- 
  

   thousandth 
  part 
  that 
  of 
  percussion, 
  in 
  the 
  case 
  we 
  have 
  been 
  considering. 
  

   The 
  work 
  of 
  shearing 
  would 
  consequently 
  not 
  be 
  greater 
  than 
  one 
  millionth 
  

   that 
  of 
  the 
  energy 
  ot 
  velocity, 
  and 
  so 
  it 
  appears 
  it 
  may 
  safely 
  be 
  disregarded. 
  

   Thus 
  in 
  the 
  case 
  of 
  such 
  a 
  partial 
  collision 
  it 
  may 
  certainly 
  be 
  accepted 
  that 
  

   those 
  parts 
  not 
  in 
  the 
  hue 
  of 
  motion 
  of 
  the 
  other 
  body 
  will 
  not 
  coalesce 
  with 
  

   the 
  other 
  body, 
  but 
  will 
  pass 
  on 
  in 
  space. 
  In 
  the 
  piece 
  struck 
  off 
  we 
  shall 
  

   have 
  partial 
  destruction 
  of 
  motion 
  in 
  space, 
  with 
  develoj)ment 
  of 
  heat 
  ; 
  

   many 
  pieces 
  will 
  fly 
  off, 
  and 
  a 
  rotary 
  motion 
  of 
  the 
  whole 
  will 
  ensue. 
  

   There 
  will 
  be 
  a 
  slight 
  pause 
  from 
  inertia, 
  then 
  the 
  powerful 
  outward 
  

   pressure 
  due 
  to 
  the 
  expansion 
  by 
  heat 
  will 
  overcome 
  all 
  resistance, 
  and 
  will 
  

   expand 
  the 
  whole 
  into 
  gas, 
  much 
  of 
  it 
  certainly 
  passing 
  beyond 
  the 
  limits 
  of 
  

   effective 
  attraction, 
  and 
  away 
  into 
  distant 
  space. 
  Let 
  us 
  pause 
  for 
  an 
  

   instant 
  to 
  examine 
  a 
  little 
  more 
  fully 
  what 
  has 
  happened. 
  

  

  Two 
  pieces 
  of 
  different 
  bodies, 
  each 
  with 
  a 
  velocity 
  of 
  about 
  500 
  miles 
  a 
  

   second, 
  have 
  coalesced, 
  but 
  although 
  the 
  motion 
  of 
  translation 
  is 
  destroyed 
  

   the 
  larger 
  part 
  of 
  each 
  side 
  of 
  the 
  mass 
  is 
  made 
  up 
  chiefly 
  of 
  one 
  of 
  the 
  two 
  

   different 
  bodies 
  : 
  as 
  these 
  are 
  moving 
  in 
  opposite 
  directions, 
  there 
  is 
  con- 
  

   sequently 
  a 
  couple 
  acting 
  on 
  the 
  mass, 
  and 
  this 
  couple 
  spins 
  the 
  mass 
  on 
  

   its 
  centre. 
  Consequently 
  many 
  pieces 
  fly 
  off, 
  and 
  are 
  followed 
  by 
  the 
  mass 
  

   of 
  gas, 
  being 
  impelled 
  outward 
  by 
  the 
  energy 
  of 
  heat 
  and 
  centrifugal 
  force 
  ; 
  

  

  