IT. Robert Mallet. ( 245 
the nature of the underlying rock-formations—an anticipation 
which has not, I am afraid, so far been fulfilled. 
In_his early views on the origin of earthquakes Mallet was in 
advance of his time. He connects earthquakes with “local 
elevations of portions of the earth’s crust, often attended with 
dislocation and fracture of the crust, and sometimes attended with 
the actual outpouring of liquid matter from beneath.” He imagines 
an earthquake to be produced “ either by the sudden flexure and 
constraint of the elastic materials forming a portion of the earth’s 
crust, or by the sudden relief of this constraint by withdrawal of 
the force, or by their giving way, and becoming fractured ”. Where 
should we look for such sudden changes ? Not in volcanic countries, 
he thinks, but rather in that broad sub-oceanic belt within which 
the deposits of the land are accumulated and from which they 
may afterwards be swept away by tidal currents. “ Such a condition 
of the sea-bottom would seem to be the most likely state of things 
to give rise to frequent and sudden local elevations or even submarine 
eruptions of molten matter.” And he notices that, while earth- 
quakes are frequent in volcanic counties, they are never of the 
oreatest violence. On the other hand, “ the centre of disturbance 
of almost all the greater earthquakes appears to be beneath the sea, 
and at considerable distances from active volcanoes,” while “ the 
circumstances of the great sea wave seem to indicate that ‘the 
centre of disturbance is seldom, if ever, very distant from the land ”. 
I have given a somewhat full account of this important memoir, 
for whatever its imperfections may be it must, I think, be regarded 
as the chief foundation-stone of seismology asa science. Fortunately 
Mallet did not rest content with this, practically his first, con- 
tribution. He became afterwards widely known to the scientific 
public by his four reports to the British Association on the facts 
of earthquake-phenomena, their publication covering most of the 
years from 1850 to 1858. His crowning work on the Neapolitan 
earthquake of 1857 was published in 1862. With this report and 
with his memoir on the velocity of earth-waves at Holyhead, his 
career as a seismologist practically ended, for his study on volcanic 
energy lies outside our range, and his later papers, owing to his 
practical blindness, were of minor value. After his first memoir 
Mallet’s work may thus be considered under the following headings : 
(i) experiments on the velocity of earth-waves ; (ii) the preparation 
and discussion of the catalogue of recorded earthquakes ; (11) 
the development of methods of investigating earthquakes; and 
(iv) their application to the study of the Neapolitan earthquake. 
Velocity of Earth-waves.—As already remarked, Mallet attached 
great importance to accurate determinations of the velocity of 
earth-waves. His first experiments were made in two widely 
differing materials—the wet sand of Killiney Bay, on the coast of 
Co. Dublin, and the granite of the neighbouring Dalkey Island. 
In Killiney Bay charges of 25 1b. of gunpowder were exploded in 
