282 ANNUAL OF SCIENTIFIC DISCOVERY. 



were prevented by a shower of stones, after which the eruptions 

 ceased, and " from that period until I left Central America, I am not 

 aware that there occurred more than one eruption, and that on the oc- 

 casion of the falling of the first considerable shower of rain, on, I 

 think, the 27th of May last. The discharges from this vent, consist- 

 ing wholly of stones, may have been and probably were peculiar, for 

 the volcanoes themselves and the cones surrounding them seem gen- 

 erally to have been made up of such stones interspersed through large 

 quantities of ashes and scoriaceous sand, alternating with beds of 

 lava. 



" Much might be said on the phenomena of earthquakes as they oc- 

 cur in this country. The shocks seem to be of two classes, the per- 

 pendicular, which are felt only in the vicinity of volcanoes, and the 

 horizontal, which reach over wide tracts of country. The latter are 

 very unequal ; in some places being violent, and in others, nearer 

 their assumed source, comparatively slight. The undulating move- 

 ment seems to be only a modification of the horizontal or vibratory. 

 Sometimes these motions are all combined, or rather succeed each 

 other with great rapidity. Such was the case with the earthquake 

 of October last, which I experienced, and of which I can speak more 

 authoritatively. 



" There are many striking features in the topography of Central 

 America, which seem entirely due to volcanic agency. Those which 

 have more particularly attracted my attention are what are popularly 

 denominated extinct craters, now partially filled with water, forming 

 lakes without outlets or apparent sources of supply save the rains. 

 Some of these occur on the mountain and hill ranges, and are sur- 

 rounded by evidences of having been volcanic vents. But this is not 

 always the case. I will take what is called the Lake of Masaga as 

 an instance. This is not less than ten or twelve miles in circumfer- 

 ence, and is not far from 1,000 feet, perhaps more, below the general 

 level of the country. The sides are sheer precipices of trachytic 

 rocks, splintered and blistered, and exhibiting every indication of hav- 

 ing been exposed to intense heat. Yet if these were true craters, 

 where are the lava, ashes, and other materials which they have eject- 

 ed 1 ? There are certainly none in their vicinity which have emanated 

 from them, no traces of lava-streams surrounding them, nor are their 

 edges elevated above the general level. Upon one side of the particu- 

 lar one which I have mentioned rises the extinct volcano of Masaga, 

 with its proper crater, whence have flowed vast quantities of lava, 

 part of which, falling near the precipitous walls of the lake, have quite 

 filled it upon that side. Some of the lakes are more or less impreg- 

 nated with saline materials, but others are perfectly fresh and abound 

 in fish. The burned and blistered walls indicate, it appears to me, 

 that they have not been caused by subsidence or the -falling in of the 

 earth or rock strata. The great plain of Leon at its highest part is 

 elevated something less than 200 feet above the sea ; yet in the vicin- 

 ity of the range of volcanoes which traverse it, beds of lava, 15 feet 

 thick, have been found in digging wells at the depth of 75 feet Span- 

 ish baras, or about 210 feet, and this at a point not the highest of the 



