Money-value of Niyht-Soil and other Manures, 127 
God's providence for the mineral stores now disclosed in luigland 
and France, and no doubt hidden elsewhere. Of the alkalies, 
he will husband his store by not selling straw, if his land be 
light and the subsoil do not contain stores of wealth in reserve. 
For carbon he may in the long run rely on the atmosphere, 
which supplies carljonic acid freely enough, however scanty may 
be its available supplies of nitrogen. As to lime, if any difliculty 
exist, it is one he can easily measure, and probably remedy at no 
great cost. In this instance a natural defect in the soil, not any 
conceivable waste of man, will generally be the obstacle to be over- 
come. Silica and silicates will puzzle him, perhaps, but not him 
only ; and he will wait till a special indictment is laid against 
him for wasting substances which do not appear to impart much 
value to granitic detritus, whether it be in the ofFscouring of our 
granite-paved streets, or the deposits borne by streams from 
primaeval mountains. And at this point he will have about 
exhausted the list of elements, which, spoken of in the abstract, 
sounds such a formidable bugbear ! 
If, however, the scientific man be consulted on a question of 
value, his natural course will then be to refer and gauge each 
new import or product by an old standard, according to the 
rates which trade and commerce indicate. 
But if it be true that what is new and of partial application 
should be gauged by that Avhich is established and familiar to all, it 
seems startling that authorities should assume, or even recognise, 
Peruvian guano as the standard of the value of manure for the pur- 
pose of comparison. Can this be historically correct ? Is it sound 
in a commercial point of view ? Men of middle age who have 
watched the rise and progress of the entire market for artificial 
manures, will recollect that, when guano first appeared, bones 
and soot were almost the only auxiliaries of farmyard-manure in 
common use. The farmer had a good notion of the value of the 
latter, but it was a composite body, so the market price of bones 
(in which phosphate predominated) and that of soot (chiefly 
valued for its ammonia) were of assistance in the difficult task of 
assessing the various elements in the straw-manure at their 
widely different money-values. The star of nitrogen was then 
in the ascendant, and accordingly the chief place was assigned to 
it — a pre-eminence not yet reversed, in spite of the overriding of 
mineral and atmospheric theories since that time. The Prices 
Current appear, on the lohole, to justify that award, being as dis- 
passionate critics of chemical philosophy as the Funds are of 
statesmanship. 
If at that time a chemist had told a farmer, " Guano is worth 
so and so, and therefore good farmyard-manure must be priced at 
12*. or 13s. per ton," would he not have been told with a smile, 
