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IV. Some Account of the Volcanic Eruption of Cosegiiina in the Bap of Fonseca, com- 
monly called the Bay of Conchagua, on the Western Coast of Central America. 
By Alexander Caldcleugh, Esq., F.R.S. F.G.S., 8$c. 
Received December 29, 1835, — Read January 7, 1836. 
There is perhaps no country on the face of the globe which shows more signs of 
vast geological disturbances than that part of the western hemisphere which, situate 
between its great northern and southern divisions, has obtained in more modern 
times the name of Central America. Its shores, extending to both oceans, are in spots 
precipitous, while other and extended lines of coast are low, and abound in man- 
grove creeks, intersected by mountains and volcanic vents, and excavated by a series 
of lakes, which in the province of Nicaragua interrupt and appear to replace the 
great chain of the Andes. The finely comminuted scoria affords a soil which pro- 
duces the richest vegetation, and a vast and new field is offered to the man of 
science who will boldly face the miasma of the forest, or penetrate the rich mines 
with which one part of the country abounds. 
At the termination of a narrow promontory, which runs in a northerly direction 
from the southern and eastern side of the Bay of Fonseca, stands the volcanic moun- 
tain of Cosegiiina, washed on three sides by the ocean, of insignificant height, and flat- 
topped ; two eruptions are on record, viz. those of the years 1709, and 1809. Since this 
last date it has remained in a state of quiescence, until the period of that stupendous 
eruption on the 20th of January last, the details of which I now beg permission to 
lay before the Royal Society. These details I have drawn up partly from official 
documents transmitted from the various towns to the government of Centro-America, 
and partly from the information of intelligent friends, eye-witnesses of all that oc- 
curred in those days of terror. The reports to the Government, which are voluminous, 
fully agree on the main points ; in others, probably owing to the changes of locality 
and consequent variation in the direction of the wind, some slight differences are ob- 
servable. It is, however, impossible to read these official reports, written too by 
persons little versed in classical learning, without being struck with the similarity of 
their description, even to the very terms he used, with that of the younger Pliny in 
relating to Tacitus the commencement of that eruption of Vesuvius which, nineteen 
centuries since, buried two cities under its ashes. 
On the 19th of January, after twenty-six years of repose, a slight noise attended 
with smoke proceeded from the mountain Cosegiiina. On the following morning 
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