This is a fact so far as the volcanic ash is concerned.  An examination of the ashes a few days ago shows that they will prove an active and valuable fertilizer.  The fertile slopes of Vesuvius have ever been an allurement to the vine-grower, four crops a year being a temptation no possible danger could drive him from, and as soon as the mountain grows surely peaceful after this eruption, we shall find its farmers risking again the chance of its uncertain temper.  But this is not the case with the land covered with lava and cinders.  Time for their disintegration is necessary before they can be brought under cultivation, and this is a matter of years.  After the great eruption of 1871-72 the land covered with cinders did not bear crops for seven years, and there is no reason that they will do so sooner on the present occasion.  So for years to come much of the volcanic soil must remain a barren and desert void.

CHAPTER XVI.

The Great Lisbon and Calabrian Earthquakes.

To our account of the great earth convulsions of San Francisco it is in place to append a description of some similar events of older date.  It is due to the same causes, whatever these causes may be, the imprisoned forces within the earth acting over great distances during the earthquake, while they are concentrated within some limited space when the volcano begins its work.  The earthquake is the most terrible to mankind of all the natural agencies of destruction.  While the volcano usually has a greater permanent effect upon surface conditions, it is, as a rule, much less destructive to human life, the earthquake often shaking down cities and burying all their inhabitants in one common grave.  Violent earthquakes are also of far more frequent occurrence than destructive volcanic eruptions, many hundreds of them having taken place during the historic period.

While the earthquake is only indirectly connected with the subject of our work, it seems desirable to make some mention of it here, at least so far as relates to those terrible convulsions whose destructiveness has given them special prominence in the history of great disasters.  Ancient notable examples are those which threw down the famous Colossus of Rhodes and the Pharos of Alexandria.  The city of Antioch was a terrible sufferer from this affliction, it having been devastated some time before the Christian era, while in the year 859 more than 15,000 of its houses were destroyed.  Of countries subject to earthquakes, Japan has been an especial sufferer, in some cases mountains or islands being elevated in association with shocks; in others, great tracts of land being swallowed up by the sea.  The number of deaths in some of these instances was enormous.

Numerous thrilling examples of the destructive work of the earthquake at various periods are on record.  Of these we have given elsewhere a tabular list of the more important, and shall confine ourselves to a few striking examples of its destructive action.  In the record of great earthquakes, one of the most famous is that which in 1755 visited the city of Lisbon, the capital of Portugal, and left that populous, place in ruin and dire distress.  It may be well to recall the details of this dire event to the memories of our readers.