of  the  Ashes  of  Plants.  499 
Per  eentage  of  water  and  ash  in  potato  oats : — 
Water. 
Ash. 
Ash  calculated 
on  dry  substance. 
No.  1. — Seed  . 
9-06  • • 
2-48 
..  2-72 
No.  2. — Produce  on  Clay- 
10-20  .. 
3-14 
. . 3-50' 
No.  3. — Produce  on  Sand  . 
10-20  •• 
3-26 
. . 3-63 
The  composition  of  these  ashes  is  given  in  the  following 
table  : — 
Composition  in  100  parts  of  the  ash  of  potato-oats: — 
No.  1. 
Seed. 
No.  2. 
Produce 
on  Clay. 
No.  3. 
Produce 
on  Sand. 
Silica 
39-75 
42-64 
46-55 
Phosphoric  Acid  . 
29  16 
28-20 
25-43 
Sulphuric  Acid 
1 - 44 
•40 
1-90 
Carbonic  Acid  . 
• • 
• • 
• • 
Lime 
3-25 
3-56 
3-76 
Magnesia  .... 
7-34 
6-47 
4-93 
Oxide  of  Iron  . . 
•74 
•53 
1-32 
Potash 
15-88 
17-42 
13-10 
Soda 
Chloride  of  Potassium  . 
2-42 
•78 
3-00 
Chloride  of  Sodium 
• • 
• • 
• • 
Total  . 
99-98 
100-00 
99-99 
The  total  sulphur  of  1000  grains  of  potato-oats  undried:  — 
Seed.  Produce  on  Clay.  Produce  on  Sand. 
2-02  • • 1-60  * ♦ . 1-72 
The  differences  in  composition  between  these  various  specimens 
are  considerable,  but  we  in  vain  seek  to  trace  them  in  any  con- 
sistent way  to  the  influence  of  the  soil.  There  can  be  no  doubt 
whatever  that  a direct  influence  is  exerted  by  the  nature  of  the 
soil,  the  manure,  and  the  season,  upon  the  mineral  characters  of 
the  different  crops;  but  a knowledge  of  these  variations  is  only  to 
Ite  arrived  at  by  joint  experiments  in  the  field  and  laboratory, 
conducted  with  great  care  and  in  the  most  varied  manner.  We 
have  before  observed  that  the  analysis  of  these  different  series 
was  undertaken  more  with  the  view  of  obtaining  sufficient  data 
for  the  average  composition  of  the  respective  crops,  than  in  the 
expectation  of  gaining  much  insight  into  the  cause  of  the  varia- 
tions to  which  they  are  subject;  although  if  any  light  could  have 
been  thrown  upon  this  part  of  the  question,  it  would  have  been 
an  additional  advantage. 
A comparison  of  the  ash  of  oats  with  that  of  wheat  would  at 
first  sight  appear  favourable  to  the  non-exhausting  character  of 
the  former.  Thus  wheat,  it  will  be  remembered,  averages  45 
