1832.J 
EARTHQUAKES. 
461 
The direction which earthquakes pursue is from south to north, 
along the chains of the Cordilleras. 
Mournful experience has s.hown, that the most violent concus- 
sions occur after an interval of about half a century, in that region 
included between the equator and the tropic of Capricorn ; and 
which seem to follow a certain order, from the extremes to the 
centre. These are the periods which- have marked the great 
earthquakes experienced since the conquest of Quito, Ariquipa, 
and Lima. The fatal period had arrived at the end of the last 
century ; and Ariquipa and the provinces of Quito were laid in 
ruins. Lima had passed the fatal period which nature appears 
to have estabhshed, but suffered in the year eighteen hundred and 
twenty-eight. 
The great earthquakes have generally been preceded by copi- 
ous rains ; the earth becoming saturated, the water penetrates into 
the interior. Hot days succeeding to these wet ones, necessarily 
form an enormous quantity of vapour, which, not being able to 
escape, or become rarefied beneath the surface of the globe, is 
exposed to the electric shock, or to become ignited from the vol- 
canoes ; when, acquiring greater expansion, it produces those 
violent convulsions of the earth, which in their effects are so ter- 
rific. Obscure exhalations rise from the earth at night, clothing 
the heavens and the stars with the most sombre pall ! 
The frequency of the earthquakes in the spring is deemed a 
good sign; as it shows the combustibles beneath are wasting 
their strength by degrees. But if these concussions are very fre- 
quent, following each other in quick succession, they indicate a 
large quantity of combustible matter, from which a violent shock 
may at any moment be expected. 
Vegetation suffers much in these gloomy epochs. The earth- 
quake of sixteen hundred and seventy-eight rendered an immense 
proportion of the soil of Peru incapable of producing wheat. The 
stalks grew luxuriantly until the head began to form, when the 
grains became affected with rust, which converted the substance 
into a black powder, and the crop was destroyed. Twenty years 
did not restore the soil to its former productiveness. Indeed, the 
injury to the agriculture of the country was fatal. In this scar- 
city, recourse was had to Chili for wheat, and that country soon 
