(3) The relations between one of the great arterial industries, such as coal-mining, railway transport, or machine-making, and a specific manufacture may be regarded as auxiliary. The extent to which the price of coal, railway rates, etc., enters into the price of the goods and affects the condition of profits in the trade measures the closeness of this auxiliary connection. In the case of the smelting industries or in the steam transport trades, even in the pottery trades, the part played by coal is so important that the relation is rather that of a primary than an auxiliary connection--_i.e._, coal-mining must be ranked as co-ordinate to smelting. But where heat is not the direct agent of manufacture, but is required to furnish steam-motor alone, as in the textile factories, the connection may be termed auxiliary.
(4) The relationship between some industries is "sympathetic" in the sense that the commodities they produce appeal to closely related tastes, or are members of a group whose consumption is related harmoniously. In foods we have the relations between bread, butter, and cheese; the relation in which sugar and salt stand to a large number of consumables. Some of these are natural relations in the sense that one supplies a corrective to some defect of the other, or that the combination enhances the satisfaction or advantage which would accrue from the consumption of each severally. In other cases the connection is more conventional, as that between alcohol and tobacco. The sporting tastes of man supply a strong sympathetic bond between many trades. The same is true of literary, artistic, or other tastes, which by the simultaneous demand which they make upon several industries, in some proportion determined by the harmonious satisfaction of their desires, throw these industries into sympathetic groups.[114] These four bonds mark an identity of interest between different industries.
The relationship is sometimes one of divergency or competition of trades. Where the same service may be supplied by two or more different commodities the trades are related by direct competition. Oil, gas, electricity, as illuminants, are a familiar example of this relationship. Many trades which produce commodities that are similar, but far from identical in character, feel this relationship very closely. The competition between various kinds of food, which with different kinds and degrees of satisfaction may produce the same substantial effects, between fish and meat, between various kinds of vegetables and drinks, enables us to realise something of the intricacy of the relations of this kind. In clothing we have antagonism of interests between the various fabrics which has led to great industrial changes. The most signal example is the rise of cotton, its triumph over woollen clothes by the earlier application of the new machinery, and over silk by the early superiority of its dyeing and printing processes.[115] So in recent years in the conflict among beverages, tea, and in a less measure cocoa, have materially damaged the growth of the coffee industry so far as English consumption is concerned. Where such rivalry exists, an industry may be as powerfully and immediately affected by a force which raises or depresses its competitor as by a force which directly affects itself.
