On the Food of Fhmf.s. 525 
certain saline inorganic substances are essential to the well-hcino; 
of i^lants in general, and of course to those we cultivate for our 
food, but unfortunately our knowledge of the kind of substance 
required in each particular case is very, very limited. Such 
knowledge, invaluable as it would prove, is only to be got by a 
long series of accurate analyses of the ashes of agricultural pro- 
duce of various kinds grown upon every variety of land and under 
every variety of circumstances — a task very unlikely to be under- 
taken by anv single individual. The illustrious Chevreul spent 
ten years in the study of some half-dozen animal fats, and his in- 
vestigation remains a perfect model of scientific research ; but it 
is little to be expected that any person in this commercial and 
manufacturing country, where applications of science to the arts 
are so well rewarded, and where abstract investigation, at least in 
chemistry, meets with so little encouragement, will devote his 
time and energies to an inquiry like the present, unless backed 
by the countenance of a public association. 
I venture to place before the Society the results of a few 
analyses of the ashes of some of the most important agricultural 
crops made during the last six months. A small number of iso- 
lated experiments like the present go but little way towards the 
settlement of the question at issue ; so far as they extend, how- 
ever, the agreement between them is complete, and they serve to 
point out a very remarkable circumstance, namely, that the dif- 
ferent parts of the same plant have the power of choice or selec- 
tion with respect to the mineral food furnished by the soil. The 
details of the processes employed are given in an appendix. 
1. Wheat grown in the Valley of the Thames, in Battersea 
Fields. 
Straw, including heads : — 
300 grains gave of ash, by incineration in a open vessel, 20*0 grains. 
300 20-8 „ 
Mean, 6*8 per cent. 
20 grains of ash gave, on analysis : — 
In 100 parts. 
Soluble salt — 
Sulphate of potash . . 2*9 . 14 'ri 
Silica . . . . 0'3 . '5 
Potash, with silica, chloride, &c. 0*4 . 2*0 
Insol. portion — 
Siliceous scales . . . 14*2 . ll'O 
Earthy phosphates . . 1*5 . 7' 5 
Carb. lime . . . 0-15 . 0 75 
Water . . . .0-2 , I'O 
Potash, magnesia, and loss . 0*35 . 1'75 
20-0 100-0 
