Indeed, before 1750, England had begun to import ship-timber from the Baltic; but it was mostly deal boards used for cabin-work, ceilings, sheathings, etc. Now she began to look to her American Colonies for the heavier materials. It was difficult to load and stow this kind of timber through the hatchways of the ships then available. The ingenuity of Philadelphia shipwrights met this obstacle by building the timbers themselves into the form of ships, and they were then navigated across the Atlantic to be broken up on arrival in British ports. These “raft-ships” were built with bluff bows and square sterns, their sides being several feet thick. To make them water-tight, they were sheathed with two thicknesses of boards which “broke joints,” and were caulked. The largest of these, called the “Baron Renfrew,” measured the equivalent of five thousand tons in a regular merchant ship. She got safely across the ocean, but went ashore on Portland Bill in a fog and broke up. Most of her timber, however, was picked up by English and French vessels which cruised for weeks in search of it. Among the mast-timber she carried was one white pine tree ninety-one feet long by four feet eight inches diameter at the butt inside the bark. This tree was used for the mainmast of the “Royal George,” a three-decker then building at Chatham (1774). It was doubtless still in the ill-fated ship when she heeled over and went down at Portsmouth in 1782. The “Baron Renfrew” was the last of the “raft-ships.” The oncoming Revolution stopped all kinds of commerce for eight years, and though after the peace ship-timber was again exported to England, it went as hold or deck cargo in regular vessels. Summing up the colonial period, it may be said that, while the records were imperfectly kept and some lost, enough is extant to show that between 1684 and 1744 one hundred and eighty-eight square-rigged ships and over seven hundred brigs and schooners, besides immense numbers of boats, river-sloops, fishing-yawls, etc., were built at Philadelphia. Her only rival in the Colonies during that period was Portsmouth, New Hampshire, but Philadelphia held the ascendency over all in the size and total tonnage of her ships. That the Colonies should have developed the ship-building industry from their earliest existence was natural and necessary. If you take a modern map of the United States and draw from Maine to Georgia a heavy black line averaging one hundred miles back from the general trend of the sea-coast, you will have in close approximation the geography of colonial settlement at its maximum. In this belt, this “narrow fringe of civilization,” were concentrated for more than a century all the energies of English-speaking pioneers, rapidly increasing in numbers and incessantly augmenting the products of enterprise and industry which, from surplus over home consumption, had to seek markets over sea.