l£ai't}(qual-es in Nicaragua. — Crawford. 115 
lu onl}' two cases have great faults cleA'eloped in the direction 
of these joint planes. One — the great Balcones fault from Austin 
to Del Rio — has a downthrow to the east and at right angles to 
the streams; except a slight deflection of the Colorado west of 
Austin, it has in no way affected the course of the streams. 
The other exceptional fault extending from Marietta, Chicka- 
saw nation to south of Texarkana has its downthrow interior- 
ward, and Red river follows its trough for many miles, and its 
direction is primarily influenced by it. 
The area is too vast to give details of many of the proposi- 
tions I have set forth, or to call attention to several minor topo- 
graphic processes. There are two agencies which cannot be 
passed, however, which play a more important factor in the Texan 
region than elsewhere in the United States, and these are wind 
and aqueous solution. Owing to aridit}^ and lack of consolida- 
tion, the crumbling structui'e is readily transported by wind, dust 
and sand storms being of great frequence. In bluffs and canons, 
composed of alternating structure of consolidated and marlj- 
layers, the former are undermined by wind erosion. 
Over the vast and intensely heated limestone plateaus, solution 
plays a most important part, and there results a remarkable 
weathering of the limestones into miniature mountain ranges, and 
a corresponding deposition of that remarkable calcareous deposit 
known in Mexico as tepetate. 
NOTES ON EARTHQUAKES IN NICARAGUA, 
FEB. 6, 1892. 
J. Cr.\wford, Leon, Micanigiui. 
At 10 h. 10 m., p. m., 6th February, 1892, occurred an ap- 
parently connected series of about 92 seconds total duration, of 
longitudinally oscillating, progressive, spherical, seismic waves 
['y=a sin (Pt — nx) . . . .] that passed northwestwardly and south- 
eastwardly in Nicaragua, parallel with, and along or near to, the 
volcanic masses which extend connectedly with but a few short 
interruptions, (as across the bay of Fonseca and lakes Managua 
and Nicaragua), between the volcanic groups in the states of Sal- 
vador and Costa Rica. 
