lative and apparently merely curious enquiry, by the mathematicians of Alexandria, into the properties of three curves formed by the intersection of a plane surface and a cone. No limit can be set to the importance, even in a purely productive and material point of view, of mere thought. Inasmuch, however, as these material fruits, though the result, are seldom the direct purpose of the pursuits of savants, nor is their remuneration in general derived from the increased production which may be caused incidentally, and mostly after a long interval, by their discoveries; this ultimate influence does not, for most of the purposes of political economy, require to be taken into consideration; and speculative thinkers are generally classed as the producers only of the books, or other useable or saleable articles, which directly emanate from them. But when (as in political economy one should always be prepared to do) we shift our point of view, and consider not individual acts, and the motives by which they are determined, but national and universal results, intellectual speculation must be looked upon as a most influential part of the productive labour of society, and the portion of its resources employed in carrying on and in remunerating such labour, as a highly productive part of its expenditure.
§ 9.In the foregoing survey of the modes of employing labour in furtherance of production, I have made little use of the popular distinction of industry into agricultural, manufacturing, and commercial. For, in truth, this division fulfils very badly the purposes of a classification. Many great branches of productive industry find no place in it, or not without much straining; for example (not to speak of hunters or fishers) the miner, the road-maker, and the sailor. The limit, too, between agricultural and manufacturing industry cannot be precisely drawn. The miller, for instance, and the baker—are they to be reckoned among agriculturists, or among manufacturers? Their occupation is in its nature manufacturing; the food has finally parted company with the
