Correspondence. ' 57 
structive to houses of any occurring in Nicaragua during the past half 
century, developing an intensity estimated by the Rossi-Forel scale 
of iv to ix, along its course from the west side of lake Managua to 
the Pacific ocean, a distance on the line of its movement of about 140 
miles. It passed through Managua, the capital of Nicaragua, at the 
rate of about 600 millimetres per second, through Leon at about 800 
mm. per second, and through the towns of Chinandega and El Vieju 
at a rapidity of wave movement or progression of about 900 mm. per 
second. 
The tile-roof covering of many houses in Managua, Leon. Chin- 
andega and El Viejo was displaced and part of the roof thrown to 
the ground, and the walls of hundreds of thick-walled, one-story, adobe 
houses were severely fissured, many beyond repair. Also the five-feet- 
thick, carefully constructed, cement and brick walls of the cathedral 
in Leon were cracked. 
Several of the volcanic formed masses and cones along the line 
of the greatest expression of the force of the first series, west of lake 
Managua, were sufficiently disturbed to cause some greater activity 
than usual in the hot mud springs near their ridges or apices and in 
the boiling springs at their bases, but there has not been exit of force 
enough at once through any volcano in the belt of seismic disturb- 
ance to cause active volcanic eruptions. 
There was no jarring motion felt, as is invariably felt when large 
areas of strata fall from the inner roof, — through gases and aqueous 
vapors at high tension and highly heated magma, — toward the floor 
of some sub-volcanic cavern or cavernous locality. Neither were any 
of the lateral movements felt, — those at an angle to the general di- 
rection of the movement of the force, — that are invariably distinct and 
frequent when the origin of the force is from a disturbed condition of 
heated materials, gases and aqueous vapors at extreme tension be- 
neath volcanic masses, as they force and fissure their way up to the 
earth's surface. 
The evident origin of the development of force in this series of 
earthquakes appears to have been from a contracting of the earth 
from loss of heat and a consequent sliding of the strata into more 
compact conditions. The waves as they developed at the earth's sur- 
face were comparatively short and high and more regular than is 
usual in earthquakes from other causes. The apex of one wave arose 
at the earth's surface beneath one wing of the large one-story building 
occupied by the bank in Managua and, parting the tile roof, caused the 
forward part of the roof to slide from its former position a distance 
of about ten feet northwardly, — along the direction that the waves of 
force were moving. The other part of the roof moved southwardly 
about eight feet. 
The first of this series of earth disturbances was preceded for a 
few seconds by a very rough grating sound, followed by a few seconds 
of tremors and slight undulations, and then severe movements undu- 
lated for about thirty seconds. 
