But besides these, and very many similar articles, throughout the whole country, and especially towards the west, immense numbers of fortresses of great size have been discovered, with walls of earth, some of them ten feet in height, and thirty in breadth. There is a vast fortress in Ohio, near the town of Newark. It is situated on an extensive plain, at the junction of two branches of the Muskingum. At the western extremity of the work stood a circular fort, containing twenty-two acres, on one side of which was an elevation thirty feet high, partly of earth and partly of stone. The circular fort was connected by walls of earth with an octagonal fort containing forty acres, the walls of which were ten feet high. At this end were eight openings or gateways about fifteen feet in width, each protected by a mound of earth on the inside. From thence four parallel walls of earth proceeded to the basin of the harbour, others extending several miles into the country, and others on the east joined to a square fort containing twenty acres, not four miles distant. From this latter fort parallel walls extended to the harbour, and others to another circular fort one mile and a half distant, containing twenty-six acres, and surrounded by an embankment from twenty-five to thirty feet high. Further north and east the elevated ground was protected by intrenchments. Traces of other walls have been found, apparently connecting these works with those thirty miles distant. When we come to reflect that there were many hundreds of similar forts, some of which were of equal size, and others even of still greater magnitude, we cannot help believing that an enormous population, considerably advanced in the arts of civilisation, must at one time have existed in the country, over which for ages past the untutored savage has roamed in almost a state of nature. And now these wild tribes are rapidly disappearing before the advancement of a still greater multitude, and a far more perfect civilisation. Whether these ancient races were the ancestors of the present Indians or not, it is difficult to determine, as are the causes of their disappearance. It is possible that, retreating southward, they established the empires of Mexico and Peru, or, overcome by more savage tribes, were ultimately exterminated. PART ONE, CHAPTER TWO. NORTH AMERICA CONSIDERED AS DIVIDED INTO FOUR ZONES, WITH THE VARIOUS OBJECTS OF INTEREST FOUND IN EACH. The North American continent may be divided into four zones or parallel regions, which, from the difference in temperature which exists between them, present a great variety both in their fauna and flora. THE FIRST ZONE.