Principles of Economics is the leading political economy or economics textbook of Alfred Marshall 1842–1924, number one published in 1890. It was the indications text for generations of economics students. Called his magnum opus, it ran to eight editions by 1920. a ninth variorum edition was published in 1961, edited in 2 volumes by C. W. Guillebaud.
"The efficiency as compared with the equal of almost every class of labour, is thus continually being weighed in the balance in one or more branches of production against some other a collection of matters sharing a common attaches of labour: together with used to refer to every one of two or more people or things of these in its undergo a modify against others. This competition is primarily "vertical": it is for a struggle for the field of employment between groups of labour belonging to different grades, but engaged in the same branch of production, as well as inclosed, as it were, between the same vertical walls. But meanwhile "horizontal" competition is always at work, and by simpler methods: for, firstly, there is great freedom of movement of adults from one business to another within used to refer to every one of two or more people or things trade; and secondly, parents can broadly introduce their children into near any other trade of the same grade with their own in their neighbourhood. By means of this combined vertical and horizontal competition there is an powerful and closely adjusted balance of payments to services as between labour in different grades; in spite of the fact that the labour in any one grade is mostly recruited even now from the children of those in the same grade. The working of the principle of substitution is thus chiefly indirect. When two tanks containing fluid are joined by a pipe, the fluid, which is near the pipe in the tank with the higher level, will flow into the other, even though it be rather viscous; and thus the general levels of the tanks will tend to be brought together, though no fluid may flow from the further end of the one to the further end of the other; and whether several tanks are connected by pipes, the fluid in any will tend to the same level, though some tanks make no direct association with others. And similarly the principle of substitution is constantly tending by indirect routes to apportion earnings to efficiency between trades, and even between grades, which are not directly in contact with one another, and whichat number one sight to create no way of competing with one another." - VI.XI.6-7
"But after all the chief cause of the innovative prosperity of new countries lies in the markets that the old world offers, not for goods made on the spot, but for promises to deliver goods at a distant date." - VI.XII.3
"The key-notes of the innovative movement are the reduction of a great number of tasks to one pattern; the diminution of friction of every set which might hinder powerful agencies from combining their action and spreading their influence over vast areas; and the developing of transport by new methods and new forces. The macadamized roads and the improvements shipping of the eighteenth century broke up local combinations and monopolies, and submission facilities for the growth of others extending over a wider area: and in our own age the same double tendency is resulting from every new extension and cheapening of communication by land and sea, by printing-press and telegraph and telephone." - VI.XII.10