Supplement to the ^'Tropical Agrieulturhty [Sei»t. 1. 1698 
one npproached tliis nitrogen question conversa- 
tionally, Voelcker's brow assumed tlie knotted 
expression well-knov^ n to his friends, and a short 
discoiir.*e would ensue, ending always in the 
reiteration that there was something or other 
which we liiid not yet taken into account, and 
without which the lialaiice was incomplete; and 
among the lasting regrets of his sons, his old 
pupils, and other survivors among his chemical 
friends, is the fact that he did not live to learn the 
discoveries of Ilelliiegel and ^Vilfarlh on the 
mode of nitrogen assimilation by the legumin- 
ous family of plants, in which discoveries ho 
would have keenly delighted. 
During my pu))iliige with him a large propor- 
tion of my time was devoted, under his direction, 
to the analysis of soils, an operation then much 
more in vogue than it now is ; and a constant 
lament poured into my youthful ear was that of 
the limit'-d utility of the analysis which we were 
called upon to make. Under some circumstances 
an aiuilysis of soil — as then and as now ordinarily 
conducted— viz., by determining the constituents 
soluble in strong mineral acids — was useful 
enough, as, for e.Kam()le,inshowingthat asoil requir- 
ed liming, in showing the pre-ence of imperfectly 
o.vidised iron, and, inferentially, the existence of 
imperfect drainage ; or as indicating a deficiency 
of phosphoric acid, of potash, or of nitrogen, so 
great as to obviously remove the soil from the 
category of ordinaiy land, and to proclaim a 
glaringly unusual degree of poverty. But under 
most circumstances it was unsatisfactory. In 
an exct-Uent paper, " 0;i the Influence of Cliemical 
Di.-coveries on the Progress of English Agricul- 
ture," publi-hed in 1878, Dr. Voelcker wrote : — 
" At one time both farmers and chemists thought 
analysis would solve all the diiBcuUie^ which 
practical men meet in cultivating soils of low 
fertility, the occupier of which experiences much 
disappointment by his frequent failure to raise 
remunerative crops upon them. 
Further experience, however, has proved that 
in many cases mere numerical analytical 
re^iults are not calculated to assist the farmer 
in improving his land, or to inform him of the 
cause of non-success in growing certain crops — 
why, for instance, he cannot grow clover on some 
soils. There are many apparently similar soils — 
that is to say, soils in which analysis shows like 
quantities of the same constituents — such as po- 
tash, sodrt, lime, magnesia, phosphoric, sulphuric, 
and silicic acids — and in which, notwithstanding, 
the same kind of manure produced a good result 
in one case and an unfavourable one in another. 
This plainly shows that the analysis of soils, as 
usually performed by chemists, does not afford 
in all cases a sufficient guide to an estimate of 
their agricultural capabilities, nor to point out 
the kind of manure which is particularly well 
adopted for the special crops intended to be 
grown. Even the detailed analysis of a soil usually 
oives only the proportions of i*-.s different consti- 
tuents, and generally without reference to the 
'trtes of combination in which they exist in the 
soil • and it is altogether silent on the property 
'>i. se-sed by all s .ils in a higher or lower degree, 
of (-iieciing striking and important changes in 
the manuies which are incorporated with the 
land. Analyses of soils, therefore, it must be 
confessed, are oftea disappoiating iu their practi- 
cal bearings." 
During the time that I worked at my bench in 
Dr, A oelcker's laboratory, some years before this, 
he iiad not only frequently talked in the bame 
strain, but had urged that any one wishing to 
make a useful contribution to 'the chemistry of 
agriculture could best do it by devoting himself 
to devising gome more subtle and more satis- 
factory means of chemically gauging the plaut- 
food iu a soil than was afforded by the ordinary 
process of determining the total pprcentoges of 
phosphates, potash, and the like, without refer- 
ence to the degree of assimilability they miglit 
happen to possess. As he often pointed oat, n 
soil containing only 1 per cent of plio>^phoric acid 
is poor rather than rich iu that constituent, as 
average soils go, yet such a soil, measured over 
an acre to a depth of from G to 9 inches, would 
contain 1 ton of phospiioric acid, which is about 
as mucli as would be contained iu 7 or 8 to.is of 
ordinary superphosphate. And yet on such a 
soil experience shows that a few 'hundredwtigbts 
of superphosphate, ujqdied at tiie i)roper time, 
make all the difference between a good and a bad 
turnip crop. 
Hermann Von Liebig (son of Justus Von Liebig) 
had tlien recently published a paper in which he 
gave the results of some attempts to distinguish 
between total ond uvailible potash iu eertuiu of 
the Rothamsted wheat-soils. He extracted the 
potash witli "dilute acetic acid ' (the use of 
which was also tried by E. Peters) and also witli 
"dilute nitric acid," but the strengths of acid 
used are not recorded. Altlnugh tlie scope of 
the investigation was not sufficiently complete to 
render the details of much practical value, the 
results, nevertheless, afforded indications that the 
enquiry might have proved of considerable interest 
had it been systematically worked out. 
Some preliminarj- work on the subject wa.s 
actually started in Dr. Voelcker's laboratory and 
under his advice, about the year 187o, beginning 
with the determination of the water-solubility of 
the constituents of a given soil, the next step in 
view being the determination of the carbonic-acid 
solubility ; but circumstances took me away 
from his laboratory before any substantial pro- 
gress was made in the matter, and it was not for 
some years that I again began to work at it, 
although the subject gradually attracted the 
attention of many chemists, some' of whose 
successive contribu' ions to it 1 have mentioned 
in the paper which appeared iu the Chemical 
Society's Journal, and these I may be allowed still 
more briefly to refer to here. 
iTo be continued.) 
INTERESTING REPORT ON INOCULATION 
AGAINST EINDERPEST. 
Since writing about Serum inoculation in 
India, we have been favoured with a copy of 
the Report on Prof. Koch's method of immaf'isi'ie 
cattle against rinderpest, issued by the Gi^ ver.Vme'nc 
of India, and embodying repai ts by Dr. Linv-urd 
Imperial Bacteriologist to the Government, of India' 
Veterinary Lieut. Baldrey, Assistant Principaii 
