THE MEDITERRANEAN NATURALIST 
only of once to twenty of sea sand and earth — 
wherever a good supply of mortar and stone was 
used the damage was most trifling even when 
the same subsoil was found below the respective 
foundations of the destroyed and uninjured houses. 
In summarising the conclusions deduced from 
my observations I find the importance of acknow- 
ledging that earthquake motion is almost entirely 
propagated upon the surface of the earth and 
not below it, is almost paramount. 
From a very elaborated series of experiments 
made at the seismologieal observatory in Japan 
to ascertain the motion of earthquake shocks on 
and below the surface a pit 18 feet deep by 4 feet 
square was constructed and the results obtained 
all tended to prove that motion was far less 
pronounced below than above the surface. 
From a careful consideration of the destructive sea 
waves which frequent by accompany earthquakes 
it seems quite certain that they are entirely caused 
by some very great displacement of water, due to 
immense land slips and subsidences at the bott mi 
of the ocean. This is especially noticeable on the 
west coast of South America, where destructive 
earthquakes invariably originate in the sea, which 
owing to its great depth and extension, have often 
caused waves to push inwards upon the coast 50 
to 100 feet in height. The volume of these waves, 
the velocity with which they travel, and the violence 
of tin- seismic disturbance are entirely dedendent 
upon the extension of the water, its depth and the 
cubic tonnage of the precipitated or subsided mat- 
ter on the sea’s bottom. 
One distinct feature, noticeable during the re- 
cent shock- was the peculiar “bumping'’ sound 
which accompanied so many of them. I his has 
been falsely attributed to an upheaval movement 
whereas it was simply the resultant motion pro- 
duced by the masses falling on to the surface from 
a lower to a greater depth in the sea. To prove 
this fact it is necessary to again refer to the seis- 
mic experiments of the Japan Society. During 
the years 1880 to 1885 a heavy ball, 1710 lbs in 
weight was made to fall from various heights. 
Subsequently many elaborate experiments were 
made with charges of dynamite and gunpowder 
exploded in bore-holes, and the results obtained 
from both these series of experiments produced 
853 
exactly the same motion hitherto described as 
upheaving in earthquakes. 
Once admitted that non-volcanic earthquake 
shocks are of a purely surface nature, then tlieir 
origin can reasonably be traced to one or all of 
the causes 1 have endeavoured to describe. 
As a further proof of the non-existence of vol- 
canoes in these parts of the Mediterranean I have 
just received t'l.e very exhaustive and splendidly 
compiled report of the work done by the Imperial 
Austrian Surveying Vessel “Pola” during the past 
three years. At intervals of every half a knot the 
depth was taken, the surface mean and bottom 
temperatures, the density of the salts, the chemi- 
cal analysis of the soil, rock etc. of the bottom 
carefully and thoroughly observed, classified and 
catalogued. Special mention is made of bottom 
and other erosive currents and the whole results 
bear out in a remarkable manner the observations 
I have alluded to at the beginning of this paper. 
In conclusion I can only express a hope that by 
drawing the attention of scientists in general to a 
logically reasonable cause for these mysterious 
and destructive visitants, a greater impetus may be 
given to seismical research by all engaged in it — 
we must always bear in mind however that we are 
dealing with a motion feeble even when intense, 
developed upon this heterogeneous mass of solids, 
liquids and gaseous components constituting our 
planet, which is spinning on its axis at the rate of 
a thousand miles an hour and speeding through 
vacuous space either ir; its orbit round the sun, at 
the rate of one thousand miles a minute, and to 
consider the enormous volume of electricity and 
electro-magnetism generated on its surface by what 
after all is nothing but a huge electrical machine, 
which may have some very close relation with the 
points at issue on seismic origin. 
Postscriptum 
Since writing this paper a most striking con- 
firmation of the marked relation between subsi- 
dence and earthquakes, has been afforded us by 
the recent landslips at Sanclgate; and although the 
affected area there is only a mile in length by a few 
hundred yards in width it appears that the whole 
of the land in this small space is more or less 
“alive” and broken up into innumerable ridges by 
the subsidences. The gaping rifts in the houses, 
