128 Transactions of the South African Philosophical Society. 
for soil analysis, can determine whether or not such infinitesimal 
amounts as are required by the crops are present, or are not present, 
in an available form in a soil,’’ and so on. 
Sir Charles Cameron, on the other hand, remarks, * ‘‘ The kind and 
amount of benefit to be derived from the analyses of soils are 
becoming every day more apparent. We cannot, indeed, from the 
results of an analysis prescribe in every case the kind of treatment 
by which a soil-may at once be rendered most productive or even 
improved. In many cases, however, certain wants of the soil are 
directly pointed out by analyses; in others, modes of treatment are 
suggested by which a greater fertility is likely to be produced, and, 
as one’s knowledge of the subject extends, we may hope to obtain, 
in every case, some useful directions for the improvement or more 
profitable culture of the land.”’ 
At one time it was suggested that all that was necessary in 
analysing a sample of soil was to reduce it to a fine powder, and 
then to take some of the powdered soil and ascertain how much, 
say, of potash, phosphoric oxide, or of lime, as the case may be, it 
contained. If much, the soil was pronounced fertile; if little, 
barren. Such was the opinion entertained by men of high eminence 
in their day: an advance, certainly, upon the opinion previously 
held, that plants were fed by water, and water alone, but an opinion 
nevertheless, capable of improvement, and improvement came. 
Baron von Liebig already saw that these views were not quite 
correct when he said—in 1858t—that soluble constituents of the soil 
sometimes entered into a kind of combination with other substances 
in the soil, and so lost their solubility, and at the same time their 
capacity for circulating about in the soil. It, was found, moreover, 
on the other hand, that from the rootlets of*plants exuded an acid 
possessing the property of acting on some of the insoluble con- 
stituents rendering them available to the plant, and in 1866 Dr. 
Cossa, Professor of Chemistry at an Italian university, pointed out} 
that if the method of determining soluble constituents in soil were to 
give trustworthy results they would have to simulate as closely as 
possible nature’s own mode of dissolving the plant-food constituents 
in the soil. It was plain that to take all that the soil contains in 
the way of potash, lime, phosphoric oxide, and nitrogen, as being so 
much plant food was erroneous, and to take only that which was 
soluble im water as being available would be no less faulty. Different 
chemists proposed different methods of settling the difficulty, but 
* Johnston and Cameron: Elements of Agricultural Chemistry and Geology, p. 3. 
+ v. Liebig: Ueber das Verhalten der Ackerkrume zu den in Wasserléslichen 
N abrungsmitteln der Pflanzen. 
{ Fresenius: Zeitschrift fiir analytische Chemie, vol. 5, p. 161. 
