May  13,  1897. 
JOURNAL  OF  HORTICULTURE  AND  COTTAGE  GARDENER 
415 
CHEMISTRY  IN  THE  GARDEN. 
{Continued  from  page  312.) 
The  fertility  of  soils  depends  to  a  considerable  extent  upon 
their  physical  properties.  The  presence  of  sand,  clay,  humus,  and 
carbonate  of  lime  has  a  great  deal  of  influence  in  determining  the 
physical  condition  of  soils,  for  each  of  these  proximate  constituents 
possess  different  properties,  and  consequently  the  character  of  a 
soil  will  depend  to  a  considerable  extent  upon  which  of  them 
predominates. 
The  Physical  Properties  of  Soils. 
The  Weight  of  Soils. — On  page  312  we  gave  the  analysis  of 
three  soils  in  parts  per  100,  or  what  is  termed  the  percentage  com¬ 
position — i.e .,  every  100  lbs.  of  soil  contains  so  many  pounds,  or 
parts  of  pound's  weight  of  certain  substances.  We  find  on 
weighing  equal  volumes  of  different  kinds  of  soil  that  the  weight  of 
each  varies  considerably.  Thus  the  approximate  weight  of — 
1  cubic  foot  of  dried  sand  is  from 
1  „ 
1) 
loam  „ 
1  „ 
1} 
clay  „ 
1  „ 
11 
leaf  mould  „ 
1  „ 
J  1 
peat  „ 
110  to  120  lbs. 
90  to  110  lbs. 
70  to  80  lbs. 
55  to  60  lbs. 
40  to  55  lbs. 
It  is  very  important  to  remember  in  considering  the  amount  of 
plant  food,  as  shown  by  the  analysis  of  a  soil,  that  although  a  «andy 
soil  may  look  to  contain  less  nitrogen,  potash,  phosphoric  acid,  and 
lime  than  a  clay,  it  may,  nevertheless,  be  the  richer  soil  owing  to  its 
greater  weight.  To  illustrate  this  fact  let  us  take,  for  an  example, 
two  soils,  each  showing  by  analysis  the  same  amount  of  phoiphoric 
acid — viz  ,  020  per  cent.  The  top  9  inches  of  an  acre  of  a  sandy 
soil  would  weigh  about  3,500,000  lbs.,  and  at  0  20  per  cent,  would 
contain  7000  lbs.  of  phosphoric  acid  ;  while  the  top  9  inches  of  an 
acre  of  a  clayey  soil  would  only  weigh  2,500,000  lbs.,  and  contain, 
at  0  20  per  cent.,  5000  lbs.  of  phosphoric  acid. 
The  term  heavy  is  often  applied  to  a  clayey  soil,  and  light  to  one 
that  is  of  a  sandy  nature.  This  is  not  literally  correct,  as  may  be 
proved  by  referring  to  the  above  table.  The  term  heavy  as  applied 
to  clayey  soils  is  used  to  denote  that  they  are  stiff,  tenacious,  and 
heavy,  or  hard  to  dig  ;  while  sandy  soils  are  called  light  became 
they  are  open,  porous,  and  light  or  easy  to  dig. 
Texture. — The  texture  of  a  soil  will  depend  upon  whether  its 
particles  are  large  or  small.  A  soil  which  is  made  up  principally  of 
coarse  particles  of  sand,  chalk,  or  stones,  possesses  little  cohesion, 
its  particles  are  large  and  loose,  and  such  soils  will  be  of  an  open, 
dry,  and  porous  nature.  If  the  particles  of  soils  are  very  minute 
the  land  will  be  of  a  close  tenacious  character,  plastic  and  sticky 
when  wet,  hard  and  lumpy  when  dry.  Soils  are  very  deceptive 
when  their  particles  are  in  a  finely  divided  state ;  thus  many  sandy 
soils  may  be  mistaken  for  clays,  a  good  example  of  this  being  the 
brick  earths  near  London.  Chalk  is  of  an  open,  porous  nature 
when  its  particles  are  moderately  large,  but  when  finely  divided  it 
possesses  a  sticky  and  retentive  character. 
Heat  of  Soils  — Nearly  the  whole  of  the  heat  of  soils  is 
derived  from  the  heat  rays  which  are  given  forth  from  the  sun. 
When  the  inn  is  shining  upon  soils  they  absorb  some  of  the  heat 
ray*,  while  others  are  radiated  into  the  air.  Some  soils  absorb 
more  heat  rays  than  others.  In  a  series  of  experiments  conducted 
by  Durocher  he  found  that  when  the  temperature  of  the  air  was 
90°  F.  a  thermometer  placed  1  inch  below  the  surface  of  different 
soils  exposed  to  the  sun  gave  the  following  results  : — Quartz  sand, 
126°  F.  ;  garden  soil,  115°  F.  ;  yellow  sandy  clay,  100°  F.  ;  chalk 
soil,  87°  F.  This  shows  us  that  a  sandy  soil  is  able  to  absorb  a  very 
large  amount  of  the  sun’s  heat,  while  a  chalk  soil  is  scarcely 
influenced  at  all  by  it.  Quartz  sand  has  the  greatest  power  of  con¬ 
ducting  heat  of  all  constituents  found  in  the  soil,  the  worst 
conductor  of  heat  being  air.  Sandy  soils,  by  being  open  and 
porous,  wdl  contain  much  air,  and  although  they  may  get  very  hot 
at  the  surface  the  heat  will  not  penetrate  to  any  depth  into  them. 
Consolidation  and  the  presence  of  stones  improves  the  conductive 
power  of  soils.  A  dark  coloured  soil  when  the  sun  is  shining  upon 
it  becomes  hotter  than  a  light  coloured  one.  This  is  shown  by  the 
fact  that  when  the  temperature  of  a  garden  soil  was  115°  F.  a 
chalk  soil  exposed  to  the  same  amount  of  *un  heat  was  only  87°  F. 
The  dark  colour  of  soils  is  generally  due  to  the  presence  of  humus, 
and  the  light  colour  to  the  presence  of  carbonate  of  lime  or  cbalk. 
It  is  very  interesting  and  instructive  to  watch  the  rapid  growth 
of  crops  growing  on  dark  coloured  soils,  while  crops  growing  under 
exactly  the  same  conditions  on  light  coloured  soils  seem  scarcely 
to  make  any  progress. 
The  presence  or  absence  of  water  chiefly  determine*  the  cold 
or  warm  nature  of  a  soil.  The  heat  required  to  raise  1  lb.  of  water 
would  raise  5  lbs.  of  quartz  sand  to  the  same  temperature,  conse¬ 
quently  it  requires  more  sunshine  to  warm  a  wet  soil  than  a  dry 
one.  Wet  soils  are  also  cold  because  the  heat,  instead  of  warming 
the  Boil,  is  used  up  in  evaporating  the  water  from  it ;  for  if  1  pint 
of  water  is  evaporated  from  100  lbs.  of  soil  the  soil  will  be  left 
10°  F.  colder  than  if  the  water  passed  away  by  filtration.  Drainage 
is,  therefore,  the  only  cure  for  a  cold  wet  soil. 
Slope  or  inclination  has  considerable  influence  on  the  tempera¬ 
ture  of  soils.  Suppose  we  have  three  soils — one  sloping  towards 
the  sun,  one  horizontal,  and  one  sloping  away  from  it.  The  first 
of  these  would  absorb  more  heat  than  either  of  the  others.  The 
AA 
N.\\ 
Fig.  85. — S,  Sun ;  R.  Heat  Rays  ;  SL,  Slope  of  Land,  (1)  towards  the  Sun, 
(2)  horizontally,  (3)  from  the  Sun. 
reason  of  this  is  that  the  same  amount  of  heat  rays  which  fall  on 
a  certain  area  of  land  sloping  towards  the  sun,  will  cover  a  wider 
area  of  land  lying  horizontally,  and  more  *o  on  land  which 
slope*  away  from  the  sun.  This  is  shown  more  clearly  in  the 
illustration  (fig.  85).  It  might  be  thought  that  the  rays  would 
diverge,  but  owing  to  the  great  size  of  the  sun,  and  long  distance 
from  the  earth,  the  heat  rays  which  reach  us  are  always  parallel. 
The  Hygroscopic  Power  of  Soils — By  thi*  term  is  meant 
the  power  soils  possess  of  absorbing  moisture  from  the  air.  It  is  a 
well  known  fact  that  if  dry  salt  be  exposed  to  the  air  it  becomes 
damp.  The  salt  has  attracted  nr  isture  from  the  air,  and  is,  there¬ 
fore,  said  to  be  a  hygroscopic  substance.  Soils  are  to  a  certain 
extent  hygroscopic  substances,  but  the  amount  of  moisture 
absorbed  is  almost  insignificant.  Scbiibler  found  by  exposing 
different  kinds  of  soil  for  twenty-four  hours  to  damp  air,  they 
absorbed  the  following  quantities  of  moisture  : — 
1000  lbs.  of  ploughed  land  absorbed  23  parts  of  moisture. 
1000  lbs.  of  clay  soil 
** 
28  „ 
1000  lbs.  of  loam 
35  i)  >i 
1000  lbs.  of  heavy  clay 
11 
41 
1000  lbs.  of  garden  soil 
52 
It  is  doubtful  if  the  hygroscopic  power  of  soils  is  due  to  the 
state  of  division  of  the  particles,  it  being  more  probably  owing 
to  the  presence  of  certain  chemical  substances  in  the  soil,  such  as 
silicates  and  hydrated  silicates  of  alumina,  and  also  to  certain 
salts. — W.  Dyke. 
(To  be  continued.) 
OUR  GARDEN. 
Times  were  when  revelling  in  the  unqualified  pride  of  possession 
our  whims  and  fancies  were  studied  by  old  Job,  plus  the  orthodox 
routine  in  which  his  soul  delighted.  Old  faslroned  to  a  fault  was  the 
worthy  man.  Peace  to  his  ashe*,  while  we  eDjoy  pleasant  memories  of 
the  past.  The  fact  that  another  gardener  was  wanted  brought  keenly 
home  to  us  that  we  were  old  fashioned,  too,  by  solicitations  shown  by 
lady  friends  that  the  new  man  should  be  different  from  the  old. 
“  Really,  Squire,  you  know  no  gardener  of  to-day  would  tolerate  such  a 
muddle  as  old  Job  delighted  in  ;  you  are  quite  behind  the  times.” 
It  was  surprising  how  many  gardeners  wanted  gardens  just  at  that  time, 
and  yet  what  a  task  it  was  in  choosing  the  right  man  for  the  right 
place. 
“So  glad,  Squire,  you  are  suited  ;  just  the  man,  I  should  think ;  now 
you  will  see  a  change.”  Prophetically  true  ware  those  words.  We 
have  seen  the  old  landmarks  disappear,  some  abruptly,  others  stealthily, 
till  a  visitor  deairing  to  be  complimentary  remarked — “The  garden  is 
so  changed  one  would  hardly  know  it.”  “  Ooe  at  least  knows  it,  and 
regrets  it,”  was  it  is  feared  a  grumpy  comment.  Still  the  fair  enthusiast 
persevered,  “  Oh  !  but  you  know,  Squire,  you  like  hardy  flowers,  and  see 
how  vastly  X  has  improved  the  long  border.”  It  is  so,  alas !  for  most 
of  our  old  favourites  are  improved  out  of  existence,  and  in  their  place 
are  the  new  “  old-fashioned  ”  flowers,  none  of  which  we  dare  gather,  and 
many  of  which  we  cannot  smell.  What  a  soul  there  used  to  be  in  that 
long  border  in  the  early  summer  mornings  ;  now  it  is  scentless — soulless, 
“  A  wonderful  collection.”  Yes,  it  is  admitted  ;  some  capped  with 
glasses  because  they  are  “  miffy,”  others  collared  with  zinc  because  they 
