PANAMA, or DARIEN, Isthmus of, connects the continents of North and South America, and forms a state of the republic of New Granada. Its shape is that of an arc of a circle, curving towards the N., and inclosing the Bay of Panamá on the S. Both sides of the isthmus are indented by several creeks and harbours, of which the most important are Port Escoces and Navy Bay on the N., and the harbours of Panamá and San Miguel on the S. The interior of the isthmus is little known. Part of it is occupied by the Cordillera, or great mountain chain which extends through the American continent; but this mountainous region is interrupted by tracts of low level ground. These plains are well watered, thickly wooded, and rich in minerals and the vegetable produce of tropical countries. Besides the railway from Aspinwall to Panamá, a canal has been proposed from Port Escoces to San Miguel. The breadth of the isthmus varies from 30 to 70 miles, being narrowest at Panamá. The chief river of Panamá is the Chagres, which flows first westward, then northward, and falls into the Atlantic, after a course of 80 or 90 miles, for 44 of which it is navigable by barges. Before the construction of the railway it was of much importance, as goods were conveyed by it part of the distance across the isthmus; and the town of Chagres, at its mouth, was the chief port on the north side of Panamá. This was, however, at best a wretchedly-built and very unhealthy place, with a shallow and unsheltered harbour, and is now quite deserted, having been supplanted by the new town of Aspinwall on Navy Bay. Pop. of the state of Panamá, 138,108.