118 The American Geologist. August, 1392 
this part of Nicaragua, a sliort series of earthquakes having oc- 
curred annually. 
There has been a subsidence, occasioning plications or foldings 
of the strata, in -u'estern Nicaragua, between the Pacific ocean 
and the line of volcanic cones, (a strip of land 27 to 33 miles 
wide,) whether paroxysmal and expressed in earthquakes or 6on- 
tinuous — has not yet been determined. This subsidence is now 
in progress, and its phenomena are being studied by the under- 
signed. J. Crawford. 
Leon, Nicaragmi, 9th Fchruary^ 1892. 
PosTSCRiPTu.M. Since mailing on 9tli instant, "Notes on Earthquake 
phenomena in Nicaragua" on 6th instant, I learn, by telegraph, as fol- 
lows, in reference to the approximate length and width of the ellipsoid 
and the line of greatest disturbance at the earth's surface: 
(a) The seismical force followed the volcanic belt southeastwardly 
into Costa Rica, and more severely south than north of the epicentrum, 
as if accummulatiug disturbing forces as it traversed the sub-terranean 
part^ of the group of active and of ''hot" volcanoes in that country 
(b) The line of greatest disturbance curved irregularly in its southern 
course — first soutbwestwardly, between the city of Rivas and the Port of 
San Jiiau del Sur, in Nicaragua, thence southeastwardly near the Pue- 
blo of Philadelphia in northern Costa Rica and along the line of vol- 
canic masses to near the city of Saa Jos6 (quite severe), thence, (so far as 
I have information to date) southeastwardly into the Caribbean sea. 
(c) The length of the disturbance of this series of seismic waves has 
been traced for over 500 miles and the average width of their disturb- 
ance about 100 miles. 
(d) Electro-magnetic phenomena, to be described hereafter, were quite 
prominent. 
(e) The retardation of the waves in— and their greater disturbance of — 
some kinds of strata can be traced at several places, also, have been noted 
a few places where they were reflected from the strata and two or three 
places where, apparently, there was interference of waves and accum- 
ulation therefrom offeree. 
(f) The focus was evidently a fissure, extending southeastwardly 
from Isla Zapatera in lake Nicaragua, for about 25 leagues into Costa 
Rica. J. Crawford. 
February 14, 1892. 
