I894-] 253 [Shaler. 
large to endure for centuries. Their deposits in the form of fine 
micaceous and other sands laid down in a stratified manner on 
the surface about the basin are likely to remain, if undisturbed by 
human agency, for many thousands of years as evidence of the 
disturbance which produced them. Similar outbreaks of water on 
a more extensive scale marked the action of the great shocks of 
the New Madrid earthquake which occurred between 1811 and 
1813. They have been observed in almost all regions where 
considerable earthquakes have occurred in districts where the 
surface was approximately level and to a considerable depth 
underlaid by incoherent materials. 
Although it may be possible by close study to determine whether 
earthquakes have occurred within a few thousand years in a 
region such as those above noted, the observation will have to 
take account of very inconsiderable phenomena, and I therefore 
fear that it will not be possible to make much use of this indication 
in determining the recent seismic history of a country. It is, how- 
ever, worth while for the observer to bear the matter in mind. 
I am inclined to think that a careful study of the alluvial country 
in our southern states may show faint traces of former shocks 
through the preservation of some of these water craters made in 
former centuries. 
The next important topographic index of earthquake shocks is 
found in the soil covering which forms on steep slopes where there 
is a considerable surface lying at angles of more tlian 25°. The 
condition of this soil covering will often give an important 
clue to the seismic history of the field. If the soil coating accu- 
mulated on this slope is of some thickness and continuity, we 
may be sure that the regions have not been subject to powerful 
shocks within the period demanded for the accumulation of the 
deposit. As long as such a slope remains unshaken, the decay of 
the rock in the subsoil and perhaps the constant falling of debris 
from the overhanging cliffs, the fragments being caught and fixed 
in the mass of vegetation, will continue the process of accumulat- 
ing the soil, but a vigorous movement of tlie region in the suc- 
cessive to and fro motion of an earthquake will certainly urge the 
mass downwards towards the base in the form of a landslide. 
Such landslides are conspicuous phenomena in all great shocks 
which occur in countries having mountainous sloj)es. Thus in the 
earthquake of 1692 on the island of Jamaica a large part of the 
