ft 
VARIETIES.  567 
This  question  is  not  only  important  in  a  medical  point  of  view  ;  it  has  a 
further  interest  from  actual  circumstances  ;  because,  by  using  unbolted 
flour  for  bread,  we  augment  the  product  at  least  a  fifth,  or  a  sixth.  The 
government  might,  consequently,  by  reducing  the  sifting  to  10  per  cent.,  as 
it  used  to  be,  cause  a  considerable  diminution  in  the  expense  of  the  food  of 
the  army,  and  that,  without  in  any  way  injuring  the  health  of  the  troops. 
Whatever  may  be  determined  on,  it  will  at  any  rate  be  acknowledged  that 
the  subject  is  worth  consideration. — Lond.  Chemist,  from  Jour,  de  Chim. 
Med. 
On  the  Assimilation  of  nitrogen  by  Plants,  and  on  the  Action  of  Nitrates  as 
Manures.    By  Thornton  J.  Herapath. 
[Extract  from  a  letter  to  Mr.  John  Watt.] 
Bear  Sir : — The  March  number  of  The  Chemist  contains  translations  of 
four  valuable  papers  by  MM.  De  Luca,  Cloez,  Harting,  and  Ville,  on  the 
assimilation  of  the  nitrogen  of  the  air  by  vegetables,  and  on  the  natural 
formation  of  nitric  acid  in  the  soil.  Having  been  for  several  years  past  en- 
gaged in  investigating  this  subject,  at  the  suggestion  of  the  late  Mr.  Pusey, 
it  may  not  perhaps  be  uninteresting  were  I  to  give  you  a  short  account  of 
the  conclusions  at  which  I  have  arrived.    They  are  as  follows  : — 
1.  That  all  soils  contain  an  appreciable  quantity  of  nitric  acid,  in  the 
form  of  alkaline  or  earthy  nitrates,  (nitrates  of  soda  or  potassa,  nitrate  of 
lime,  or  nitrate  of  ammonia.) 
2.  That  some  soils  contain  a  much  larger  proportion  of  these  salts  than 
others  do. 
3.  That  some  fertile  soils  contain  as  much  as  3  to  6-1000ths  of  alkaline 
or  earthy  nitrates. 
4.  That  the  presence  of  these  salts  in  the  soil  is  to  be  ascribed  partly  to 
the  presence  of  the  nitric  acid,  and  nitrate  of  ammonia  in  rain  water,  and 
partly  to  the  formation  of  nitric  acid,  from  the  spontaneous  oxidation  of 
the  nitrogen  of  the  air,  and  of  that  of  decomposing  animal  and  vrgetable 
matters,  present  in  the  soil,  or  added  to  it  in  shape  of  manure. 
5.  That  some  soils  possess  the  power  of  transforming  free  nitrogen  and 
nascent  nitrogen  into  nitric  acid,  in  a  higher  degree  than  others. 
6.  That  light  porous  soils  generally  effect  nitrification  more  readily  than 
dense  and  heavy  soils. 
7.  That,  coeter is  paribus,  a  larger  proportion  of  nitric  acid  is  produced  in 
hot,  than  in  cold  weather. 
8.  That  the  fertility  of  soil  for  certain  plants  appears  to  be  caused  by 
those  soils  possessing  this  property  of  transforming  nitrogen  into  nitric  acid 
in  an  eminent  degree. 
9.  That  nitrogen  in  the  form  of  nitric  acid,  in  general,  acts  better  as  a 
manure,  than  nitrogen  in  the  form  of  ammonia. 
10.  That  nitrogen  usually  acts  best  as  a  manure  when  in  the  form  of 
