44  Air.  hunter  on  the  Heat , &c. 
power  of  refitting  it,  and  of  not  allowing  their  cold  to  be 
brought  much  lower. 
To  fee  how  far  vegetables  are  fimilar  to  tliofe  animals 
in  this  refpedt,  I made  feveral  experiments : I however 
fafpedled  them  not  to  be  fimilar,  becaufe  fuch  animals 
will  die  in  a cold  in  which  vegetables  do  live;  I therefore 
fuppofed  that  there  is  fome  other  principle. 
I did  not  confine  thefe  experiments  to  the  walnut 
tree,  but  made  fimilar  ones  on  feveral  trees  of  different 
kinds,  as  pines,  yews,  poplars,  &c.  to  fee  what  was  the 
difference  in  different  kinds  of  trees.  The  difference 
proved  not  to  be  great,  not  above  a degree  or  two : how- 
ever, this  difference,  although  fmall,  fliews  a principle  in 
life,  all  other  things  being  equal ; for  as  the  fame  expe- 
riments were  made  on  a dead  tree,  which  flood  with  its 
roots  in  the  ground,  fimilar  to  the  living  ones,  they  be- 
came more  conclufive. 
In  October  I began  the  experiments  upon  the  walnut 
tree,  when  its  powers  of  action  were  upon  the  decline, 
and  when  it  was  going  into  its  paflive  life. 
exp.  vi.  October  18th,  at  half  paft  fix  in  the  morn- 
ing, the  atmofphere  at  5 i°f,  the  thermometer  in  the 
tree  was  at  55°^;  but,  on  withdrawing  and  expofing  i 
for  a few  minutes  in  the  common  atmofphere,  it  fell 
to  So°i. 
EXP, 
