﻿528 
  Dr. 
  H. 
  Wilde 
  on 
  the 
  Moving 
  Force 
  of 
  Terrestrial 
  and 
  

  

  law 
  of 
  the 
  attraction 
  of 
  gravitation, 
  tbe 
  truth 
  of 
  which 
  could 
  

   at 
  once 
  be 
  perceived 
  by 
  a 
  simple 
  mental 
  calculation. 
  Thus 
  

   60x60 
  = 
  3600 
  is 
  the 
  attractive 
  force 
  at 
  the 
  earth's 
  surface, 
  

  

  and 
  reciprocally 
  - 
  — 
  7777: 
  at 
  the 
  distance 
  o£ 
  the 
  moon's 
  orbit. 
  

   ^ 
  -^ 
  5b00 
  

  

  Now 
  this 
  same 
  demonstration 
  is 
  equally 
  applicable 
  to 
  the 
  

  

  quantity 
  of 
  moving 
  force 
  of 
  terrestrial 
  bodies 
  as 
  well 
  as 
  at 
  

  

  the 
  distance 
  of 
  the 
  moon's 
  orbit. 
  For 
  as 
  the 
  moving 
  force 
  is 
  as 
  

  

  the 
  square 
  of 
  the 
  velocity, 
  a 
  body 
  falling 
  during 
  one 
  minute 
  

  

  through 
  a 
  distance 
  of 
  16 
  feet 
  1 
  inch 
  at 
  the 
  moon's 
  orbit^ 
  that 
  

  

  is 
  to 
  say, 
  with 
  a 
  velocity 
  60 
  times 
  less 
  than 
  at 
  the 
  earth's 
  

  

  surface, 
  its 
  moving 
  force 
  would 
  be 
  60 
  X 
  60 
  = 
  3600 
  times 
  less 
  

  

  than 
  that 
  of 
  a 
  body 
  falling 
  the 
  same 
  distance 
  during 
  one 
  

  

  second 
  of 
  time 
  on 
  the 
  terrestrial 
  globe. 
  ThereforQ 
  the 
  

  

  moving 
  force 
  and 
  the 
  attraction 
  of 
  gravitation 
  are 
  alike 
  

  

  inversely 
  proportional 
  to 
  the 
  square 
  of 
  the 
  distance,, 
  and 
  are 
  

  

  correlated 
  equally 
  in 
  amount 
  to 
  maintain 
  and 
  retain 
  the 
  moon 
  

  

  in 
  its 
  orbit 
  during 
  the 
  course 
  of 
  its 
  revolution 
  round 
  the 
  

  

  earth. 
  

  

  14. 
  The 
  quantitative 
  relations 
  of 
  the 
  moving 
  and 
  attractive 
  

   forces 
  of 
  the 
  planetary 
  bodies 
  are 
  set 
  forth 
  in 
  the 
  following- 
  

   new 
  calculus 
  of 
  elements, 
  wherein 
  Mercury 
  is 
  taken 
  as 
  unity 
  

   instead 
  of 
  the 
  Earth, 
  as 
  in 
  ordinary 
  astronomical 
  tables. 
  

  

  15. 
  The 
  masses 
  of 
  the 
  bodies 
  are 
  taken 
  as 
  equal 
  and 
  require 
  

   to 
  be 
  multiplied 
  by 
  the 
  specific 
  mass 
  of 
  each 
  planet 
  for 
  the 
  

   total 
  force. 
  

  

  16. 
  As 
  the 
  moving 
  and 
  attractive 
  forces 
  are 
  correlatively 
  

   equal 
  they 
  are 
  expressed 
  by 
  the 
  same 
  numbers 
  and 
  their 
  re- 
  

   ciprocals, 
  Mercury 
  = 
  1*000, 
  and 
  Neptune 
  = 
  -^^ 
  = 
  0*00016, 
  

  

  as 
  in 
  the 
  similar 
  calculus 
  of 
  moving 
  and 
  attractive 
  forces 
  of 
  

   the 
  moon 
  during 
  its 
  orbital 
  revolution. 
  

  

  17. 
  The 
  planetary 
  distances 
  in 
  radii 
  of 
  that 
  of 
  Mercury 
  

   may 
  be 
  taken 
  as 
  astronomically 
  correct, 
  as 
  they 
  are 
  derived 
  

   from 
  the 
  periodic 
  times 
  ; 
  but 
  the 
  numerical 
  expression 
  of 
  

   them 
  in 
  miles 
  is 
  necessarily 
  only 
  a 
  near 
  approximation, 
  from 
  

   the 
  fact 
  that 
  the 
  value 
  of 
  the 
  unit 
  of 
  distance 
  has 
  not 
  yet 
  

   been 
  exactly 
  determined. 
  Accepting, 
  provisionally, 
  the 
  unit 
  

   distance 
  of 
  Mercury 
  to 
  be 
  35,860,000 
  miles, 
  we 
  have 
  for 
  the 
  

   mean 
  distance 
  of 
  the 
  Earth 
  from 
  the 
  Sun 
  2-583 
  x 
  35,860,000 
  

   = 
  92,626,380 
  miles, 
  and 
  of 
  Neptune 
  77-59x35,860,000 
  

   = 
  2,782,377,400 
  miles. 
  In 
  like 
  manner 
  the 
  intermediate 
  

   planetary 
  distances 
  in 
  miles 
  may 
  also 
  be 
  determined. 
  

  

  