34 REPORT—1845. 
decomposition of the humus. He pointed out, how the mere introduction of healthy 
plants into a soil might aid in rendering the phosphates and alkaline salts, locked up 
within the latter, more speedily soluble, and hence inferred that a larger amount of 
these substances might be extracted where the plants were stimulated into activity by 
the presence of decomposing organic matter. He also was led to inquire whether, in 
the event of a scantier supply of one of the alkalies or of the earths than was common, 
a plant would substitute ad libitum another which might be presented to it in greater 
abundance. To determine this, he obtained from Mr. Way, late assistant to Professor 
Graham, an analysis of three samples of six different kinds of crop, viz. potatoes, 
barley, turnips, hemp, flax, and beans; one sample being that cultivated for ten suc- 
cessive years in the same ground without manure; the second from a similar plot 
which had grown different crops for the same period without manure; the third from 
a plot in a contiguous part of the garden which had been recently manured. From 
the results obtained, it would appear that the aggregate amount of bases, in the three 
samples, was about the same; but the proportion of these bases one to the other varied 
considerably, a circumstance at first sight appearing to confirm the theory of substi- 
tution. ‘The author, however, conceives, that this may be explained by supposing a 
different degree of developmentof the several parts or proximate principles in the respec- 
tive samples, as he finds a great discrepancy in the amount of phosphoric acid present 
in gluten and in starch, and thinks it probable that the same diversity may extend to 
other of the principles contained in each plant. ‘That potass is better adapted for the 
organization of a plant than soda, seems to follow from the circumstance, that whilst 
the soil usually contained an excess of soda, the plant always was most rich in potass, 
The author, therefore, in accordance with the views of Liebig, throws out as a con- 
jecture, that the soda found in the ash may be that circulating through the vegetable 
tissue, and contained in the sap, whilst the potass is actually assimilated, and consti- 
tutes a part of the vegetable tissue. ‘Ihe former, as Liebig supposes, may be useful 
in conveying carbonic acid to the plant, but cannot be substituted for potass, at least 
without injury to its healthy condition. It appears also, from the analyses referred 
to, that land-plants have not the power of decomposing common salt; so that this 
substance cannot, as has been supposed, be serviceable to vegetation by affording a 
supply of alkali. We may also infer, that it does not follow, because a soil is benefited 
by manuring, that it is destitute of the ingredients which the manure supplies, since it 
may happen that these ingredients are present in the soil in an insoluble, and there- 
fore not in an available condition. Chemical and mechanical means may no doubt be 
effectual in bringing into a soluble condition the phosphates and alkaline salts thus 
locked up within the soil, but as this is brought about by Nature herself, we might 
often spare ourselves the necessity of resorting to such means, if we would only re- 
solve not to counteract her beneficial agency, by suffering to run to waste the various 
excrementitious matters which she has placed at our disposal. The analyses given, 
from their great discrepancy with those of Sprengel, may also show the importance of 
that investigation of the constituents of the ashes of plants, which is now about to be 
undertaken under the auspices of the Royal Agricultural Society. ‘The author also 
conceived that the line of research which he had pursued might be useful, in illus- 
trating that system of scientific book-keeping which he had proposed at a former 
meeting of the Association, at once as an useful exercise to the agricultural student, 
and as a means of introducing greater precision into the conduct of our experiments 
on such subjects. ' 
On the Chemical Principles of Rotation of Crops. By Professor Jounston. 
On the Analysis of the Ashes of Plants. 
By J. Tuomas Way, Professor of Chemistry, Royal Agricultural College. 
The method here described was that pursued by the author in the analyses which 
are detailed in Dr. Daubeny’s paper “On the Rotation of Crops,” (see p.33). It 
is founded on that of Will and Fresenius (Chemical Memoirs, part ix.), but differs 
in several essential particulars, more especially in the estimation of the phosphoric 
acid. 
Two hundred grs. of the prepared ash are dissolved in hydrochloric acid. The so- 
