DARIEN, Isthmus of, a neck of land which unites North and South America, composed of the provinces of Panama and Veragua, belonging to the republic of Colombia. It sweeps in the form of a crescent about the great Bay of Panama on the south, and has the Gulf of Mexico on the north. It is about 300 miles long, and generally about sixty wide, but where narrowest, between the ports of Porto Bello and Panama, only thirty-seven. This part is sometimes called the Isthmus of Panama. The country here is made up of sickly valleys and stupendous mountains, which seem to be placed as eternal barriers between the Atlantic and Pacific Oceans, which can be distinctly seen at the same time from the summits. These mountains render it impracticable to cut a canal here, but by going to latitude 12° N. and joining the head of the lake Nicaragua to a small river which runs into the Pacific Ocean, and forming a canal thirty miles long, through a low level country, a communication might be formed between the two seas.