of  the  Ashes  of  Plants.  501 
Mean  mineral  composition  of  oats  and  oat-straw  : — 
Mean  of  3 Spe- 
cimens of  Hope- 
ton  Oats. 
Mean  of  3 Spe- 
cimens of 
Potato-Oats. 
Mean  of  6 Spe- 
cimens of  Oats 
(Hopeton  and 
Potato). 
Mean  of  3 Spe- 
cimens of 
Oat  Straw. 
Percentage  of  Ash 
305 
2-96 
3-00 
4-64 
Silica  .... 
47-08 
42-98 
45-03 
49-56 
Phosphoric  Acid  . 
22-69 
27-60 
25-14 
5-07 
Sulphuric  Acid  . 
2-25 
1-25 
1*75 
3-35 
Carbonic  Acid 
•45 
— 
•23 
1-36 
| Lime 
3-67 
3-52 
3-59 
7-01 
‘ Magnesia  .... 
6-39 
6-25 
6-32 
3-79 
Peroxide  of  Iron  . 
•82 
•86 
•84 
1-49 
Potash  .... 
14-78 
15-47 
15-13 
19-46 
Soda 
•99 
2-07 
1-53 
1-93 
Chloride  of  Potassium 
— 
— 
— 
2-71 
Chloride  of  Sodium  . 
•88 
— 
•44 
4-27 
Total  . . 
100-00 
100-00 
100-00 
100-00 
In  the  two  first  columns  of  the  table  the  averages  of  Hopeton 
and  potato-oats  are  contrasted.  The  third  and  fourth  columns 
give  the  average  composition  of  all  the  specimens  examined. 
We  have  before  observed  that  the  difference  in  composition 
between  the  ash  of  oats  and  wheat  is  (with  the  exception  of  silica) 
rather  apparent  than  real.  A very  simple  calculation,  founded  on 
the  preceding  table,  will  serve  to  prove  this  proposition  in  the 
case  of  the  most  important  constituents — the  potash  and  phos- 
phoric acid.  The  grain  of  wheat,  on  an  average  of  a great  number 
of  specimens,  contains  1*67  of  ash,  of  which  45 ‘00  per  cent,  is 
phosphoric  acid  and  31  ‘37  is  potash. 
The  grain  of  oats  gives  an  average  of  3-00  per  cent,  of  ash,  of 
which  25'  14  per  cent,  is  phosphoric  acid  and  15*13  potash  ; or 
only  about  half  the  per  centage  quantities  of  each  that  occur  in 
the  ash  of  wheat.  Mark  now  the  similarity  when  a given  weight 
of  each  grain  is  compared  : — 
Phosphoric  Acid.  Potash. 
1000  lbs.  of  wheat,  at  1 -0/  of  ash,  4a  per  cent,  of 
which  is  phosphoric  acid  and  31-  S7  potash, 
will  contain 7 '52  • • 5' 24 
1000  lbs.  of  oats,  at  3-00  per  cent,  of  ash,  of  which 
25-14  per  cent,  is  phosphoric  acid  and  15' 13 
per  cent,  potash,  will  contain 7'54  •*  4-54 
So  that  equal  weights  of  wheat  and  oats  will  require  an  amount  of 
phosphoric  acid  and  potash  which  for  practical  purposes  may  be 
looked  upon  as  identical. 
The  following  quantities  of  the  different  mineral  matters  are  taken 
up  bv  a fair  crop  of  oats,  the  straw  being  supposed  to  be  about  half 
as  much  again  in  weight  as  the  grain.  48  bushels  of  oats,  at  42  lbs. 
to  the  bushel,  will  weigh  2016  lbs.,  containing  60'5  lbs.  of  ash. 
3024  lbs.  of  straw  and  chaff  will  contain  138‘4  lbs.  of  ash  : — - 
