A building material that came into use earlier than granite is known as freestone or sandstone; although its first employment does not date back further than the erection of King's Chapel, Boston, already referred to as the earliest well-known occasion where granite was used in building. Altogether the most famous American sandstone quarries are those at Portland, on the Connecticut River, opposite Middletown. These were worked before the Revolution; and their product has been shipped to many distant points in the country. The long rows of "brownstone fronts" in New York city are mostly of Portland stone, though in many cases the walls are chiefly of brick covered with thin layers of the stone. The old red sandstone of the Connecticut valley is distinguished in geology for the discovery of gigantic fossil footprints of birds, first noticed in the Portland quarries in 1802. Some of these footprints measured ten to sixteen inches, and they were from four to six feet apart. The sandstone of Belleville, N.J., has also extensive use and reputation. Trinity Church in New York city and the Boston Atheneum are built of the product of these quarries; St. Lawrence County, New York, is noted also for a fine bed of sandstone. At Potsdam it is exposed to a depth of seventy feet. There are places though, in New England, New York, and Eastern Pennsylvania, where a depth of three hundred feet has been reached. The Potsdam sandstone is often split to the thinness of an inch. It hardens by exposure, and is often used for smelting furnace hearth-stones. Shawangunk Mountain, in Ulster County, yields a sandstone of inferior quality, which has been unsuccessfully tried for paving; as it wears very unevenly. From Ulster, Greene, and Albany Counties sandstone slabs for sidewalks are extensively quarried for city use; the principal outlets of these sections being Kingston, Saugerties, Coxsackie, Bristol, and New Baltimore, on the Hudson. In this region quantities amounting to millions of square feet are taken out in large sheets, which are often sawed into the sizes desired. The vicinity of Medina, in Western New York, yields a sandstone extensively used in that section for paving and curbing, and a little for building. A rather poor quality of this stone has been found along the Potomac, and some of it was used in the erection of the old Capitol building at Washington. Ohio yields a sandstone that is of a light gray color; Berea, Amherst, Vermilion, and Massillon are the chief points of production. St. Genevieve, Mo., yields a stone of fine grain of a light straw color, which is quite equal to the famous Caen stone of France. The Lake Superior sandstones are dark and coarse grained, but strong.