29s  Papers  relative  to  an  Accident 
arife  from  a difference  in  the  quantity  of  metallic  matter 
contained  in  the  refpeCtive  fubftitutes ; becaufe  the  tin- 
foil  which  covered  the  great  cylinder  (independent  of 
the  nails  and  wood  it  contained)  was  found  to  be  near 
three  times  heavier  than  the  weight  of  the  whole  wire. 
Neither  could  thefe  differences  be  owing  to  a dif- 
ference in  the  quantity  of  furface  of  the  refpective  fub- 
ftitutes ; becaufe  the  furface  of  the  great  cylinder  was 
found  to  be  ten  times,  greater  than  the  furface  of  the 
wire.. 
Thofe  feveral  differences  muft  therefore  depend  upon 
fome  other  caufe;  and,  as  a true  knowledge  of  this  caufe 
may  be  of  fome  moment  in  the  prefent  inquiry,  we  muft 
endeavour  to  find  it  out  by  experiments  and  obfervations. 
To  this  end  it  may  be  neceffary,  that  our  inquiry 
fhould  begin  from  an  early  part  of  this  fubjeCt,  fo  that 
we  may  proceed  regularly,  ftep  by  ftep,  as  nature  direCts. 
By  purfuing  this  method  (though  it  is  propofed  to  be 
done  very  generally  on  account  of  the  length  of  this 
paper)  we  may  poflibly  arrive  at  the  knowledge  of  the 
caufe  in  queftion,  and  fhorten  the  road  to  the  main  ob- 
ject in  view ; I mean,  the  effects  of  comparative  velocities. 
From  the  nature  of  this  fubtile  and  elaftic  fluid,  and 
its  being  diffufed  throughout  the  whole  earth  as  well  as 
4 the 
