_. Soils of the South-Western Districts of the Cape Colony. 129 
there was no organised mode of solving the problem until, early in 
_the seventies, the Congress of German Experiment Stations took up 
the matter. Numerous experiments were carried on in laboratories. 
all over the country, and side by side with each of these experiments 
the soil itself was directly appealed to by actual cultivation. The 
outcome of these investigations was that the agricultural chemists 
of Germany, assembled in congress, resolved to adopt certain fixed 
methods of analysing the soil in such a manner as to approach as 
closely as possible to natural processes; and this they did, first of 
all, not by pounding the soil, but by szfting it, and so excluding from 
the portion actually analysed big fragments of bone and other 
materials that would give a fictitious value to the soil, and would be 
of too large size to be successfully dealt with by the acids excreted 
from the plants’ roots. A fixed weight of the sifted soil was then 
taken for analysis, treated with a definite quantity of diluted hydro- 
chloric acid of a certain strength for a stipulated time at a fixed 
temperature and under specified conditions. Subsequently it was 
found that, in order to extract the variably available phosphoric 
oxide, different solvents would be necessary; and for this specific 
purpose water was used, and a solution of citric acid in ammonia. 
liquor. By these means three “grades,” if the expression may be 
applied, of phosphoric oxide are distinguished. The most imme- 
diately valuable part is that which dissolves when a definite weight 
of soil is continwously shaken with a certain volume of water for 
half an hour ; next, that soluble under specified conditions in the: 
ammonium citrate solution; and lastly, that insoluble in the latter 
solution, These methods, which found their chief exponent in the 
experiment station at Halle, gained such worldwide repute that, at. 
the special request of the United States Department of Agriculture, 
they were published in book form in 1892. This, as already 
observed, was the first attempt to organise methods of soil analysis. 
- into a practically applicable code. Since then the official agri- 
cultural chemists of the United States have also adopted a pro- 
visional uniform method, thus following the lead of Germany, 
France, Italy, and even Russia have in turn followed up, and the. 
‘United States, in the person of Dr. Wiley,* have rendered great. 
service by collating all the methods in use, and thus _inter- 
national agreement on the subject has been brought appreciably 
nearer. In England there has been no organised attempt to deal 
with the matter, and many analysts are still content to follow 
ancient methods; no wonder, then, that one sometimes hears soil 
analysis cried down. In 1894, however, Dr, Bernard Dyer recom- 
* Wiley: Principles and Practice of Agricultural Analysis, vol. i... 
9 
