SECRETARY'S REPORT. 107 



the ingredients of that soil may be in such a state of mechanical 

 aggregation as to be scarcely at all available to the absorptive 

 apparatus of the plant. The conditions of atmosphere, of 

 moisture, and of temperature, affected always by the character 

 of the soil as to its mechanical composition, will have a most 

 marked and sometimes entirely controlling influence in regard 

 to the production of vegetable growth. So important is this, 

 that, some twenty years ago, I undertook, in association with 

 my youngest brother, a vefy prolonged series of investigations, 

 having an agricultural object in view, with the purpose of 

 ascertaining somewhat numerically and with necessary exact- 

 ness, the degree to which the solubility, and therefore the avail- 

 ableness, of certain mineral materials was affected by the 

 reduction of those substances to a state of extremely fine 

 comminution, and here are some of the results. 



A mass of granite, which yields to rain water or to distilled 

 water an entirely imperceptible trace of any of its ingredients by 

 contact, will, when it has been reduced by a properly continued 

 process of reduction, to an impalpable powder, — even finer in 

 these experiments than wheaten flour, — at once begin to suffer 

 decomposition by the contact of pure water ; so much so, that 

 a little of this powder placed in a paper funnel, and then 

 exposed to the dripping, for a short time, of perfectly pure 

 water passing through it, will yield up a sufficient amount of its 

 potash, its soda, and of its lime, to make it perfectly easy to 

 demonstrate tlieir presence in the liquid when received in a 

 vessel beneath, by the appropriate tests. And so a mass of 

 felspar, a mass of hornblende, a mass of soapstone, or a mass of 

 the hardest sienite, when thus reduced to a very fine condition 

 of comminution will be found instantly to show the decomposing 

 action of the infiltrating water ; and when that water is 

 charged with carbonic acid, which it must be when it descends 

 in rain drops through tlie atmosphere, drinking up this gas as it 

 passes down, and still more as it sinks through the earth, it 

 has a double, even a tenfold power of solution in regard to 

 these various materials. Now see the difference in another 

 case. We take an ordinary mass of bone-earth, which has been 

 broken into the form of bone meal, by the common process of 

 Bogardus's mill ; we know that to a certain extent, it is soluble 

 by the infiltrating water that passes through it. But let this 



