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Rh Managua; Masaya or Popocatepac (which was active in 1670, 1782, 1857 and 1902, and attains a height of 2972 ft.), and Mombacho (4593 ft.), near Granada; lastly, in Lake Nicaragua the two islands of Zapatera and Ometepe or Omotepec with its twin peaks Ometepe (5643 ft.) and Madera. On the 20th of January 1835 Coseguina was the scene of one of the most tremendous eruptions on record. The outbreak lasted four days and the volcanic dust and ashes erupted fell over a vast area, which comprised Jamaica, southern Mexico and Bogota. After a long repose Ometepe also burst into renewed activity on the 19th of June 1883, when the lavas from a new crater began to overflow and continued for seven days to spread in various directions over the whole island. In the Maribios district occur several volcanic lakelets, such as that of Masaya, besides numerous infernillos, low craters or peaks still emitting sulphurous vapour and smoke, and at night often lighting up the whole land with bluish flames.

In the great lacustrine depression of Nicaragua is collected all the drainage from the eastern versant of the volcanic mountains, from the sheer western escarpment of the main cordillera, and from a large area of northern Costa Rica. The only river which flows out of the depression on the north enters the Bay of Fonseca at Tempisque. The accumulated waters which pour down into the depression are gathered into the two basins of Lake Managua and Lake Nicaragua. Both basins have a maximum depth of some 260 ft. Lake Managua, the more northerly, has a length of 30 m. and varies in breadth from 8 to 16 m. Its area is about 575 sq. m. After the rains a portion of its overflow escapes southwards into the lower and larger Lake Nicaragua, through the Panaloya channel. Steamers ply on both lakes, but the channel is rendered impassable by a rapid near the town of Tipitapa, at its northern extremity. Here there is a waterfall of 13 ft. The existence of ancient lacustrine beaches, upheaved between the two basins by volcanic agencies or left dry by some enlargement of the San Juan outfall, and a consequent subsidence of the water-level, seems to indicate that the lakes were formerly united. Now, however, Lake Managua is almost a closed basin in the dry season, when the stream in parts of the Panaloya channel sinks to a mere rivulet. The surface of Lake Nicaragua after the rains is 110 ft. above sea-level. The lake is 100 m. long, and has a maximum breadth of 45 m. and an area of 2970 sq. m. It is thus the largest sheet of fresh water between Lake Michigan and Lake Titicaca on the borders of Bolivia and Peru. Towards the San Juan outlet its depth decreases to 6 or 8 ft., owing to the vast accumulation of the silt washed down into the lake by its principal Costa Rican affluent, the Rio Frio. Much of this silt is again carried away by the San Juan. Under the influence of the intermittent trade-winds Lake Nicaragua rises and falls regularly, whence the popular notion that it was a tidal lake. It is also exposed to the dangerous Papagayos tornadoes, caused by the prevailing north-easterly winds meeting opposite currents from the Pacific. It is drained on the south by the San Juan river. which flows generally east by south to the Caribbean Sea. The distance from the lake to the principal or Colorado mouth of the river is 95 m., and the average width of the channel 1500 ft. Near its mouth the main stream branches out into a wide delta. Navigation is greatly impeded by shifting banks of silt, and especially by five rapids which can only be traversed when the river is in full flood. It is often asserted that these rapids were artificially formed by the Spaniards themselves to prevent the buccaneers from penetrating to Lake Nicaragua. But Herrera (Dec. iii. book 2, chap. 3) speaks of the “great rocks and falls” which prevented Cordova, the first circumnavigator of the lake, from descending the San Juan in 1522; and although the English traveller Gage states that in his time (17th century) vessels reached Granada direct from Spain, there can be little doubt that the rapids are natural obstructions, The various schemes which have been put forward for the conversion of the San juan and the lacustrine depression into an interoceanic waterway are fully discussed under.

The main Nicaraguan cordillera, which flanks the depression on the east, has often been called the Cordillera de los Andes, from its supposed continuity with the mountain-chains of Panama and the west coast of South America. There is in fact no such continuity, for the San Juan valley completely separates the mountains of Panama from the main Nicaraguan system. This severance, it is true, may be geologically recent, and some geologists see, in the five rapids of the San Juan, remnants of a connecting ridge which the river has swept away. But the evidence for past continuity is inconclusive, while there can be no doubt about the present severance of the two mountain systems. The main cordillera bears different names in different parts of Nicaragua. Thus the important section which terminates at Monkey Point is commonly called the Cordillera de Yolaina. The summits of the main cordillera seem nowhere to exceed 7000 ft. in altitude; the mean elevation is probably less than 2000 ft.; the declivity is sheer towards the lakes, and gradual towards the Caribbean. Along the shores of the lakes the cordillera may be described as a double range, consisting of two series of ridges divided by a great longitudinal valley. The lower series, which adjoins the lakes, rises near Lake Managua, and marches parallel to the main crest of the cordillera as far as the northern base of the Yolaina section; it then diverges, trending south-east nearly as far as Greytown, while the axis of, the Yolaina section has a more easterly direction.

On the east, the main cordillera abuts upon the region of plateaus and savannas, which occupies nearly half of the area of Nicaragua. It is likely that this region was once a single uniform tableland, sloping by degrees to the flat Mosquito Coast, in which direction its level still sinks. But the relief of the tableland has been wholly changed by fluvial action. The great rivers which flow eastward to the sea have fissured and moulded the surface into deep ravines alternating with high plateaus, ridges and isolated hills. Large tracts of these uplands have never been adequately explored, and consist of virgin forest and prairie. The principal river is the Segovia, which rises in the main cordillera due north of Lake Managua, winds E.N.E. as far as 85° W., and constitutes the frontier until it reaches the sea at Cape Gracias à Dios, after a course of more than 450 m., during which it receives many tributaries. Its basin is narrow and its volume not remarkable, but in length it surpasses all other Central American rivers. Its nomenclature, like that of many lesser streams in the plateau region, is somewhat confusing; for while the Spanish colonists were settling beside its headwaters the mid-stream was hardly known except to the native Indians, and the lower reaches were frequented by buccaneers, often of British or Dutch origin. In addition to the three names of Segovia, Coco or Cocos, and Wanks, which are applicable to the whole river, different parts have from time to time received the names of Cabullal, Cabrugal, Cape River, Encuentro, Gracias, Herbias, Oro, Pantasma, Portillo Liso, Tapacac, Telpaneca, Somoro, Yankes, Yare and Yoro. Other important streams, all flowing to the Caribbean in a direction E. by S., are the Hueso, Wawa, Cuculaia, Prinzapolca, Rio Grande, Bluefields and Rama. The Rio Grande or Amaltara, which receives one large tributary, the Tuma, is navigable for about 100 m. The Bluefields, Blewfields, Escondida, or Rio del Desastre, which derives its best-known name from that of Blieveldt, a Dutch Corsair, is navigable for 65 m. The hydrography of Nicaragua is curious in two respects: as in the Amazonian region all the large rivers flow east, none escaping to the Pacific; and the main watershed does not correspond with the main cordillera, which is inferior in this particular both to the volcanic mountains and to the plateau region.

The geology, fauna and flora of Nicaragua may be studied in connexion with those of the neighbouring countries (see ).

Climate.—The climate is mild and healthy for Europeans on the uplands, such as those of Segovia and Chontales, which have a mean elevation of 2000 to 3000 ft. above sea-level. But elsewhere it is distinctly tropical, with two seasons—wet from May to November on the Pacific slope, and from June to December on the Caribbean, and dry throughout the winter months. The mean annual temperature is about 80° Fahr., falling to 70° at night and rising to 90° at noon in summer. Nicaragua comes within the zone of the wet north-east trade-winds, which sweep inland from the Atlantic. The rainfall is heavy along the west side of the lacustrine basin, with an annual mean at Rivas of 102 in., but this figure is sometimes greatly exceeded on the east coast, where rain is common even in the dry season. Observations made at Greytown in 1890 showed the extremes of temperature to be 89° Fahr. in September for the maximum and 70° Fahr. in January for the minimum; the rainfall for the whole year amounted to 297 in., the rainiest month having been July (52·5 in.) and the driest, May (4·9 in.). Earthquakes are felt at times on the Pacific slope, but in Nicaragua they are less violent than in the neighbouring countries.

Inhabitants.—Accurate statistics as to the growth and distribution of the population cannot be obtained, and the figures given below are based on estimates which can only be approximately correct. The census of 1882 gave the total as 275,816; this appears to have risen in 1890 to 375,000, in 1900 to 500,000, and in 1905 to 550,000, or 11 inhabitants per sq. m. There can thus be no doubt that the population is increasing with extraordinary rapidity, although there is hardly any immigration. The number of Europeans and their pure-blooded descendants is about 1200, and tends to increase. Spanish and German elements preponderate in the foreign colonies. The most densely peopled region and the focus of civilization is the lacustrine depression and the surrounding uplands. Here are all the large towns, and hither European settlers were attracted from the first by the temperate climate, rich soil, and natural waterways. The development of Nicaragua, unlike that of most American countries (notably Brazil and the United States), has been from west to east. The great mass of the population is a composite race, descended chiefly from the native “Indians,” their Spanish conquerors, many of whom were Galicians, and the negro slaves introduced during the colonial period. Intermarriage with British, Dutch, and French with Caribs and Creoles has further complicated the ethnology of the country, producing “Indians” with fair hair and blue eyes, and half-castes with European features and Indian or negroid coloration, or with European