ON  CHEMISTRY  APPLIED  TO  THE  ARTS.  259 
lying  locked  up  and  motionless  in  these  forms  for  indefinite 
periods,  phosphorus,  by  further  geological  movements  becomes 
again  exposed  to  the  action  of  its  natural  solvents,  water  and  car- 
bonic acid,  and  is  thus  restored  to  active  service  in  the  organisms 
of  plants  and  lower  animals,  through  which  it  passes,  to  complete 
the  mighty  cycle  of  its  movements  into  the  blood  and  tissues  of 
the  human  frame.  While  circulating  thus,  age  after  age,  through 
the  three  kingdoms  of  nature,  phosphorus  is  never  for  a  moment 
free.  It  is  throughout  retained  in  combination  with  oxygen,  and 
with  the  earthy  or  alkaline  metals  for  which  its  attraction  is  in- 
tense." After  these  eminently  philosophical  views  by  Dr.  Hof- 
mann,  I  will  proceed  to  call  your  attention  to  the  application  of 
bones  to  agriculture.  Bones  are  generally  used  for  manuring  in 
one  of  these  three  forms, — 1st.  As  ground  green  bones  ;  2d.  As 
ground  boiled  bones — (that  is,  bones  nearly  deprived  of  their  os- 
seine  by  boiling  under  pressure,  as  I  shall  describe  in  my  next 
lecture) ;  3d.  Superphosphate  of  Lime. 
Green  or  raw  bones  have  been  used  on  grass  land  for  a  long 
period,  but  their  action  is  exceedingly  slow  and  progressive, 
owing  to  the  resistance  of  the  organic  matter  to  decomposition 
and  the  consequently  slow  solubility  of  the  phosphate  of  lime  in 
carbonic  acid  dissolved  in  water.  What  substantiates  this  view 
is  that  boiled  bones  are  far  more  active  than  the  above.  It  is 
found  that  30  to  35  cwts.  per  acre  of  these  will  increase  the  crops 
on  pasture  land  from  10  to  20  per  cent,  in  the  second  year  of 
their  application.  But  the  great  advantage  which  agriculture 
has  derived  from  the  application  of  bones  as  a  manure  has  arisen 
from  their  transformation  into  superphosphate  of  lime,  especially 
application  to  root  and  cereal  crops.  To  Baron  Liebig  is  due  the 
honor  of  having  first  called  the  attention  of  farmers  (in  1840)  to 
the  importance  of  transforming  the  insoluble  phosphate  of  lime 
of  bones  into  the  soluble  superphosphate,  rendering  it  susceptible 
of  immediate  absorption  by  the  roots  of  plants,  and  of  becoming 
at  once  available  for  their  growth.  These  suggestions  of  Liebig 
were  rapidly  carried  out  on  a  practical  scale  by  Messrs.  Mus- 
pratt,  of  Lancashire,  and  J.  B.  Lawes,  of  Middlesex ;  and  in 
consequence  of  the  valuable  results  obtained  by  them,  the  man- 
ufacture of  artificial  manures  has  gradually  grown  into  an  im- 
portant branch  of  manufacture  in  this  country.  The  manufactuer 
