2i  ti  Dr.  white’s  Experiments 
The  air  had  then  contracted  a noifome  fmell,  like  a 
new-cleaned  ditch,  and  was  diminiihed  from  62°  to  49°. 
Several  experiments  gave  the  fame  refults:  on  handing 
longer,  it  was  diminiihed  from  62°  to  290. 
This  experiment  proves  and  illuftrates  the  effects  of 
moifture  co-operating  with  unhealthy  foils  in  producing 
their  pernicious  effects.  Moifture  to  a certain  degree  is 
necefi'ary  to  every  kind  of  fermentation ; hence  I fufpect, 
that  by  the  falling  of  a certain  quantity  of  rain  upon 
marfhy  grounds,  a fermentation  immediately  commences 
in  the  putrid  foil,  a quantity  of  vitiated  particles  are  let 
at  liberty,  by  which  the  air  is  polluted.  Tec  degree  of 
fermentation  is  influenced  by  the  degree  of  heat,  and  the 
greater  or  lefs  quantity  of  moifture. 
exp.  xxiv.  To  the  mud  ufed  in  the  laft  experiment,  fo 
much  more  water  was  added  as  to  dilute  it  fo  that,  upon 
fubfiding,  a confiderable  height  of  water  fwam  above  it; 
it  was  confined  with  the  air,  and  flood  as  in  the  laft 
experiment. 
The  air  being  then  tried  by  the  teft,  it  was  in  no  in- 
ftance  found  farther  diminiihed  than  from  62°  to  56°. 
This  experiment  was  made  with  a view  of  difcovering 
the  effect  of  marfhes  and  bogs  when  laid  under  water; 
and  we  find  that  their  danger  is  in  a great  meafure  ob- 
viated by  it:  fo  that  the  putrid  fermentation  is  either 
prevented 
