•045

•051

•369
•403
•0403
■0679


De  Saussure's  analyses  show  that  there  is
more  carbonic  acid  on  the  mountains  than  in
the  plains,  as  might  be  inferred  from  the  com-
parative absence  of  vegetation  in  elevated
positions.  Dr  Pietra  Santa  states  that  the  air
of  hills  or  mountains,  at  the  height  of  2300
feet,  is  lighter  than  common  air,  contains  a
smaller  proportion  of  oxygen,  and  is  impreg-
nated with  a  largely  increased  amount  of
aqueous  vapour.  It  also  contains  a  large
quantity  of  ozone.  He  considers  such  a  cli-
mate peculiarly  soothing  to  persons  suffering
from  chest  diseases.
Dr  Angus  Smith's  analysis  of  the  air  from
the  mountainous  districts  of  Scotland  confirms
the  above  statement  of  Dr  Pietra  Santa's.
The  heaths  and  mountains  of  that  country
are  remarltably  healthy  localities,  and  the  air
from  them  gave  on  analysis  20'94  per  cent,  by
vol.  of  oxygen,  and  only  "033  of  carbonic
acid.
Ammonia  is  derived  from  the  putrefaction
of  animal  and  vegetable  substances.  It  is
from  atmospheric  ammoniacal  compounds  that
plants  obtain  much  of  the  nitrogen  which  is
essential  to  the  formation  of  many  parts  of
their  structure.
Nitric  acid,  like  ammonia,  is  absorbed,  and
its  nitrogen  assimilated,  by  plants.
In  addition  to  the  gases  and  vaponrs  already
enumerated,  as  well  as  others  which  exist  in
minute  quantity,  or  which  are  of  only  occa-
sional occurrence,  Pastenr  and  other  investi-
gators have  discovered  in  the  air  living  germs
which  are  capable  of  exciting  putrefaction
and  fermentation,  and  which  are  competent,
in  some  instances,  to  engender  disease  when
they  are  injected  into  the  blood  of  animals.
In  fact,  the  spread  of  infectious  diseases,
e.g.,  smallpox,  typhus  fever,  cattle  plague,
&c.,  is  attributed  to  the  presence  in  the
atmosphere  of  the  germs  of  such  maladies.
