Analyses of Ashes of Plants. 
675 
per cent, is silica, leaving 1*51 per cent, of other bodies. In 100 
parts of this ash we have by calculation 
Phosphoric acid . . . 47 '10 
Mfignesia . . . . 11 -00 
Lime 2 -20 
Potash 30-80 
Soda 6-83 
which is very similar to the composition of wheat ash. Weight 
for weight, then, barley contains quite as much phosphoric acid, 
magnesia, and alkalies as wheat, in addition to a large proportion 
of silica. 
The silica and the per centage of ash are both higher in oats 
than in barley. The internal mineral matter, when the silica is 
deducted, will be found to be as rich in alkalies and phosphoric 
acid as wheat. 
Tile ash of oats, making this deduction of the silica, will contain 
in 100 parts — 
Phosphoric acid . . . 43 '00 
Magnesia . . . . 17*00 
Potash . . . . 28-00 
Soda 3-00 
This circumstance in the mineral history of both barley and 
oats has a most important bearing on considerations of a practical 
nature; for were the weight of either of these crops equal 
to that of a crop of wheat, they >vould exhaust the land to an 
equal if not greater extent than the latter. Tliis is not quite the 
case; but still the relative amoiuit of mineral matter removed in 
the three cereals is by no means so different as is generally sup- 
posed. We have endeavoured to draw out something like an 
average of the three crops and their mineral matter. Let us 
suppose that we have land of such character as to produce an 
average crop of either — that is, for an acre, 
45 busliels of oats at 42 lbs. = 1890 lbs. ; and at 2 • CO per cent, ash = 49 lbs. 
mineral matter. 
40 bushels of barley at 48 lbs. = 1920 lbs. ; and at 2-20 per cent, ash = 42 lbs. 
mineral matter. 
30 bushels of wheat at 61 lbs. = 1830 lbs. ; and at 1 -67 per cent, ash = 30 lbs. 
mineral matter. 
The mineral matter of these crops, omitting substances of little 
importance, would consist of in lbs. 
Phosplioric Acid. Magnesia. Potasli and Soda. Silica. 
Wheat. . 13-5 .. 3-6 .. 10-2 .. 1-5 
Barley . . 13-4 .. 3-0 .. 10-5 .. 12-5 
OaU . . lO'O ,. 4-3 .. 7-5 .. 25-0 
Here it will be seen that oats (as regards mineral matters) are, 
upon the supposition of the above being averages, rather less 
