276 REPORtT—1905. 
Valuable as recent developments of soil analysis may havé been (and 
I allude in particular to the improvements in the methods of mechanical 
ahalysis which have been worked out in the United States Department 
of Agriculture, to the many investigations that have been made on the 
measurement of ‘available’ plant-food by attack with weak avid solvents, 
to the determinations of the bacterial activity of the soil) the results they 
yield can only be truly interpreted when they can be compared with a 
riass of data accuinulated by the use of the same methods on known 
Boils. 
One of the service’, then, which the farmers in every country may very 
properly expect from the scientific man is such a survey of the principal 
soil types, affording the necessary datum lines by which the comparative 
richness and poverty of any particular soil may be gauged. In an old 
settled country like the United Kingdom such a survey would guide the 
farmer in his selection of manures ; in a new country the advantages 
would be even more apparent, as the areas appropriate to particular crops 
would be indicated, and settlers would be saved from many expensive 
attempts to introduce things for which their land was unsuited. 
It would also be possible to indicate the measures which should be 
taken to ameliorate the nature of the poorer soils, for, remote as may now 
seem the prospects of spending time and labour on bad land in new 
countries where there is still a choice of good, once the road to improve- 
ment is indicated little by little the work will be done. It is hardly 
realised to what extent the soils in England have been ‘made’; the 
practice of ‘chalking,’ previously mentioned as having doubled or trebled 
the value of the Rothamsted land, must have added between 100 tons 
and 200 tons of chalk per acre to those soils before the end of the 
eighteenth century, and in other parts of the country marling, claying, 
incorporation of burnt earth and other lighter material have contributed 
enormously to render the present degree of fertility possible. 
The main facts of the nutrition of the plant have been so long 
established that it is not always realised how much still remains unknown. 
It has become a commonplace of the textbooks that the plant needs 
nitrogen, phosphoric acid, potash, often in excess of the quantities present 
in anormal soil ; so that these substances alone are considered of manurial 
value, other necessary materials like lime, magnesia, iron, sulphuric acid, 
and chlorine being practically never Jacking under natural conditions. 
But the function of these substances in the development of particular 
plants, the manner in which the character of the crop is affected by an 
excess or a deficit, is still imperfectly apprehended. We realise the 
dependence of vegetative development upon the supply of nitrogen, and 
how an excess defers maturity ; we are also beginning to gather facts as 
to the manner in which an overplus of nitrogen causes alterations in the 
structure of the tissues and variations in composition of the cell contents 
that resuit in increased susceptibility to fungoid attack. Again, it is clear 
that potash takes a fundamental part in the process of assimilation, the 
production of carbohydrate in all forms being dependent on the supply of 
potash ; but of the manner or the location of the action we have no 
knowledge. Our ignorance of the function of phosphoric acid is even 
greater ; broadly speaking, it hastens maturity, and is bound up with 
such final processes in the plant’s development as the elaboration of 
seed. With this we naturally correlate on @ priori grounds the pre- 
sence of phosphorus in the nucleo-proteids ; but there is no particular 
