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first source, that of primitive chemical affinity, is scarcely used at all, 
since the elements (with the partial exception of sulphur) are desired 
for the sake of other properties than their capacity of yielding energy. 
The next portion of the same table, that intended for the arrange- 
ment of our knowledge of the substances used, not for the produc- 
tion of energy, hut for the sake of their physical, chemical, 
physiological, or other properties, may most simply be divided 
according as the substances are animal, vegetable, or mineral. The 
mineral sources may conveniently be grouped as non-metallic, 
metallic, rocks, and soils ; the vegetable and animal by natural 
groups. But the matter and energy seized from nature are mere 
raw materials, as yet unfitted for application to the maintenance of 
the society. From this state, in which they may be termed poten- 
tial products, they must be developed into that of ultimate products. 
And a little consideration will show that this process of develop- 
ment has generally three stages, — the first, of exploitation, including 
agriculture, mining, engineering, &c. ; the second, of manufacture ; 
the third, of movement by the agencies of transport and exchange 
to the place of ultimate application to the wants of the society — pro- 
tection, alimentation, nervous stimulus, &c. These propositions are 
exhibited and somewhat extended in Table B 1.* 
§ 15. In complex societies, however, a large proportion of raw 
materials has to be converted into apparatus for service in exploita- 
tion, manufacture, and transport; these may be termed mediate 
products. We have now the main principles of an exhaustive classi- 
fication of all products whatsoever ; thus — 
a. Potential Products. 
See Table B 1. 
j3. Mediate Products , used in — - 
1. Exploitation. 
2. Manufacture. 
3. Movement. 
(a) Transport. 
(b) Trade. 
y. Ultimate Products, f 
* This table is essentially borrowed from Tait and Balfour Stewart. See 
Balfour Stewart, “ Elementary Treatise on Heat.” 
t The details of the above classification would involve the printing of a con- 
