DOWN along the Battery sea-wall is the place to watch the ships go by. Coastwise schooners, lumber-laden, which can get far up the river under their own sail; big, full-rigged clipper ships that have to be towed from the lower bay, their topmasts down in order to scrape under the Brooklyn Bridge; barques, brigs, brigantines-all sorts of sailing craft, with cargoes from all seas, and flying the flags of all nations.