THE PRINCIPLES OF BOTANY. 
913 
can see how it is that he gets the best crop of barley after 
roots which have been grown with both artificial manure and 
farmyard dung ; this is shown by the large per-centages of 
potash and phosphoric acid. As regards the magnesia, Pro- 
fessor Yoelcker remarks: “ One of the most marked ingre- 
dients is magnesia, which, though it exists in all cereals, 
seems to be especially abundant in barley. This accounts 
for the fact that barley is generally successfully cultivated 
on magnesian limestones, and points to the advantage of 
supplying magnesia when it is deficient in the manure/'’ 
Now, as all limestones contain more or less of magnesia, 
the success of barley- growing on cornbrash, whose very name 
is derived from the fact that it is, even though a brash, good 
for corn, this point will be made clear by the following 
analysis of cornbrash, which was kindly performed for us by 
Professor Yoelcker, in order to elucidate some geo-agricultural 
facts in connection with this rock. 
Analysis of Cornbrash. 
Grains. 
Carbonate of lime 
. 89T95 
Magnesia 
•771 
Sulphate of lime .... 
•241 
Alumina 
2-978 
Phosphoric acid .... 
T77 
Soluble silica .... 
P231 
Insoluble siliceous matter 
4-827 < 
Alkaline salts .... 
. Undetermined 
99-420 
Now, though doctors may differ about the administration 
of their medicines, there seems every reason to believe from 
these data that the vegetable physiologist, the chemist, and 
the intelligent farmer will all agree that sulphate of magnesia 
— Epsom salts ! — may at least be beneficially employed in 
dosing barley land. 
It now only remains to point out that barley straw is also 
much used for feeding purposes. Its air-dried proximate 
composition may be quoted as follows : 
Nitrogenous organic matter 
. 170 
Organic matter free from nitrogen . 
. 8212 
Ashes 
. 5-24 
Water 
. 10*94 
100-00 
This is mixed both for cattle and horses with havy and cut 
into chaff, and both do well upon it if they have a little corn. 
Cattle are kept on barley straw in strawyards all the winter, 
and too many on it alone ; it is, however, bad economy, as 
