The Wealth of Nations by Part 4 Chapter 7 Page 237

subordinate branches which must be carried on, in order to carry on the principal one. But when a nation is ripe for any great branch of trade, some merchants naturally turn their capitals towards the principal, and some towards the subordinate branches of it; and though all the different branches of it are in this manner carried on, yet it very seldom happens that they are all carried on by the capital of one private merchant. If a nation, therefore, is ripe for the East India trade, a certain portion of its capital will naturally divide itself among all the different branches of that trade. Some of its merchants will find it for their interest to reside in the East Indies, and to employ their capitals there in providing goods for the ships which are to be sent out by other merchants who reside in Europe.