#14 On the Physical Analysts of Soils. Marcu, 
proper to conduct us to the object of our research. It is ip fact by 
this method that we acquire a knowledge of the degree of force 
with which the soil retains heat, a power on which its specific heat 
and its conducting faculty depend. ‘This method is likewise much 
easier and more certain than the two first when applied to the soils. 
It is by the difference in the time during which they retain their 
heat that great masses of soil are chiefly distinguished in nature. 
The two last columns contain the relation of the different soils 
with respect to electricity and galvanism. When the dry earths 
are scraped with a knife, and the scrapings allowed to fall upon the 
plate of an electrometer, they all, even humus, exhibit negative 
electricity. When perfectly dried they are non-conductors, ex- 
cepting argillaceous earths, which are semi-conductors, owing to 
the iron and the humidity of which they are never totally deprived. 
With respect to galvanism the humus is distinguished from the 
other soils in a remarkable manner. The ordinary soils are all on 
the negative side of the galvanic column; humus alone is on the 
other side. I employed humus dissolved in different menstrua, 
namely, water, lime-water, potash, or soda-water, or water im- 
pregnated- with sulphate of lime. In all these cases the humus 
was precipitated in brown flocks round the positive pole. This 
often teok place in a few minutes, while the alkalies and earths 
were collected round the negative pole. I conceive it to be im- 
portant to attend to these galvanic relations of the earths, before 
preceeding to their chemical decomposition, as for example, that 
of humus into carbon and different gases, and of the earths into 
metals and oxygen. Would it be impossible to form a galvanie 
pile by alternate arrangements of humus and the other arable 
soils? I have not hitherto been able to procure a sufficient quantity 
of humus to try the experiment. The galvanic phenomena above 
indicated were obtained by means of piles of 45 pair of plates, 
each an inch in diameter. 
These details I conceive will enable you to judge of my experi- 
ments. For my own part I am satisfied that the chemical analysis 
of any fertile soil whatever would not be sufficient to make us 
acquainted with it in all its relations, and to assign it its true place 
in agriculture : for the physical properties of soils composed of the 
same chemical constituents may be very different, according to the 
different forms and modes in which the simple earths are combined 
in the different compound soils, from which important phenomena 
result, of which all the species of soils furnish examples. 
Far from considering my researches on phenomena so interesting 
to vegetation and agriculture as terminated, I have resolved (as far 
at least as depends upon myself) to continue them, without neg- 
Jecting any thing which may lead to more general and certain 
results. At present I am employed in further experiments on the 
absorption of oxygen by the earths; on the different degrees of heat 
which they acquire from light; and on their different influence in a 
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