3G4 
On  the  Power  of  Soils  to  absorb  Manure. 
singular  fact  that  putrid  urine,  when  filtered  through  a soil, 
was  deprived  of  colour  and  smell,  and  reduced  in  external  cha- 
racters to  the  condition  of  ordinary  water.  The  destruction 
of  colour  and  smell  would,  of  course,  imply  either  an  alteration 
or  a total  abstraction  from  the  urine  of  those  substances  to  which 
these  qualities  are  due.  Now,  since  all  putrid  smells  are  more 
or  less  connected  with  the  presence  of  nitrogenic  matter  in  a 
state  of  change,  it  would  become  a matter  of  great  importance  to 
decide  to  which  of  the  above  causes  the  purification  was  due. 
If  by  filtration  through  a soil  the  animal  matters  of  urine  were 
merely  altered — transformed,  for  instance,  into  nitric  acid — they 
need  not  necessarily  (and,  in  the  case  of  nitric  acid  just  stated, 
decidedly  would  not)  be  retained  by  the  soil.  But  numberless 
observations  in  practical  agriculture  would,  when  rightly  inter- 
preted, lead  us  to  believe  that  fertile  soils  have  the  power  of 
arresting  matters  containing  nitrogen,  and  retaining  them  in  such 
a form  that  in  due  time  they  become  available  as  food  for  plants. 
I am  unable  to  give  more  than  a general  sketch  of  the  property 
of  soils  to  combine  with  the  organic  portion  of  manure,  but  the 
experiments  that  have  now  to  be  described,  though  inadequate  to 
explain  the  cause,  sufficiently  establish  the  fact,  and  they  must  be 
received  as  an  earnest  of  the  rich  reward  awaiting  the  further 
prosecution  of  this  most  interesting  research. 
Experiments  in  Filtering  Putrid  Urine. 
Experiment  92. — Two  filtering  tubes,  each  24  inches  long,  were  filled  to 
the  depth  of  18  inches  with  Mr.  Huxtahle;s  light  soil.  Upon  these  filter- 
beds  a quantity  of  highly  offensive  stinking  tank  water  was  poured.  Owing, 
however,  to  the  fineness  of  the  soil,  and  to  a sedimentary  deposit  from  the 
liquid  at  the  surface  of  the  soil,  the  filtration  was  very  slow,  and  at  the 
end  of  3G  hours  none  of  the  liquid  had  passed.  The  soil  was  then  pushed 
out  of  the  tubes.  The  liquid  had  so  far  penetrated  the  filter  that  the  por- 
tions near  the  bottom  were  quite  wet,  but  they  exhibited  no  smell,  and  it 
was  not  till  12  inches  of  the  wet  soil  had  been  ejected  that  any,  even  the 
smallest,  smell  of  the  urine  was  perceptible. 
Experiment  93. — The  same  soil  was  mixed  with  its  own  weight  of  white 
sand  to  make  it  more  permeable ; in  other  respects  the  experiment  being 
made  in  the  same  way  as  the  last.  The  liquid  did  not  pass  for  several 
hours,  but  ultimately  more  than  1 ounce  of  it  passed,  quite  clear , free  from 
smell  or  taste , except  a peculiar  earthy  smell  and  taste  derived  from  the 
soil.  It  contained  no  ammonia,  as  would  be  expected  from  experiments 
already  described,  but  salts  of  lime  in  considerable  quantity. 
These  experiments  sufficiently  corroborate  Mr.  Huxtable’s 
observation  of  the  action  of  a soil  upon  the  colouring  matters  and 
substances  producing  smell  of  putrid  urine.  They  have  been 
repeated  with  many  different  soils  and  under  every  possible  com- 
bination of  circumstances,  but  still  with  the  same  effect.  It  would 
be  tedious  and  useless  to  relate  all  these  experiments  in  detail,  and 
it  may  be  sufficient  to  state  that  similar  results  were  obtained  by 
