AVAILABILITY OF POTASH IN GROUND ROCK. 15 



cost for freijiLit and carriage and tho nsc of horse and cart would amount to only 

 oue-tweutk'th. TLerefore we can afford to pay unhesitatingly a hi^hei- price for 

 the finest stone uieal that has been passed thronjih a sieve than for an article 

 that may he not so much a line powder hut rather a kind of coarse sand. 



Inasmuch as this bulletin is interested mainly with the inquiry con- 

 cerning the use of fine-ground feldspar or feldspathic rocks known to 

 be rich in potash, no greater space need be given the (rerman stone 

 meal discussion. 



Some experiments were carried out in 1887 on the use of ground 

 feldspar as a fertilizer by Aitken, a Scotch agriculturist, and chemist 

 to the Highland and Agricultural Society of Scotland. Aitken does 

 not say that he was aware of the work of ^Magnus or the deductions 

 of Hensel. The record of these experiments is given in the author's 

 own words : " 



We are familiar with the fact that feldsiiar, under the slow but constant 

 action of those forces included under the name of weathering, becomes dis- 

 intejijrated and decomposed, and that the potash it contains is dissolvetl away 

 from it by rain, so that streams emanatiu},' from districts where feldspathic 

 rocks abound are found to contain potash salts, and the level straths laid down 

 by the prolonged action of these streams yield fertile soils that are rich in 

 potash. These soils are the product of natural agencies that have been going 

 on for centuries, and the store of soluble potash salts they contain has been 

 increased to an untold extent by the sl.ow solvent action of the roots of plants 

 that have grown on them, so that the conversion of feldspathic rock into soil 

 so rich in potash as to afford an abundant supply of that constituent for the 

 raising of agricultural crops is the product of the work of centuries. At first 

 sight, it might seem a foolish thing to expect that by merely grinding felds- 

 pathic rock, and strewing the powder upon soils deficient in potash, the long 

 natural process referred to should be so accelerated as to cause the feldspar 

 to act as a source of potash for the immediate u.se of the growing of crops 

 whose vigorous growth demands a relatively large amount of that substance. 

 Nevertheless, the striking results of an experiment made at the society's ex- 

 periment station at Pumpherston showed that such an expectation w^as not 

 altogether unreasonable. Ground phosphates had been used as a phosphatic 

 manure with varying success for some years, and as it seemed that the vary- 

 ing nature of the results obtained might be due to the varying degrees of fine- 

 ness to which phosphates were ground. I made a small preliminary experiment, 

 in which the same phosphate was applied in different degrees of fineness, and 

 I found that the more finely ground the phosphate the more effective was it as 

 a manure. A similar experiment on a larger scale is described in the present 

 volume of the Transactions, page 245, where it is seen that the etficiency of 

 ground phosphates is in direct proportion to their fineness. It therefore seemed 

 reasonable to suppose that feldspar, although it is a very insoluble substance, 

 might, if it were ground to an exceedingly fine powder in certain circumstances, 

 be found to yield to the action of the solvents in the soil and in the roots of 

 plants so rapidly as to be available as a source of potash to some crops, even 

 during the short period of a single season. 



Accordingly I obtained, through Mr. Bodker, the Swedish and Norwegian con- 

 sul here, at whose instigation the experiment was undertaken, a supply of very 



« Trans. Highland and Agr. Soc. Scotland, 1887, ser. 4, 19, 253. 

 104 



