ON THE FACTS OF EARTHQUAKE PHENOMENA. 53 
land or softening it by lateral action, as in newly-formed rivers and 
__ lakes, and thus producing slips. 
The following are some of my reasons for this conclusion. The limits of 
elasticity of none of the soft materials of which plains of clay, &c. consist, and 
indeed of none of the incoherent formations that we are acquainted with, are 
sufficiently great to permit of the formation of fissures of the width and size 
upon record. The fissures that have been carefully observed have always 
been found parallel to great escarpments or to lands that have slipped; thus 
all the observers of the Calabrian earthquake concur in stating that the great 
fissures were parallel to the faces of the steep banks of the ravines or valleys, 
and more numerous the nearer they approached them; and those curious 
‘radiating fissures at Jerocarne, which are alluded to and figured by Sir 
Charles Lyell, are probably no exception, but most likely arose from the 
ground having fallen away in all directions around, which it would do if cir- 
eumstanced as an insulated mass, surrounded wholly or on three sides by the 
usual deep gorges with precipitous sides, of the Calabrian plain. I cannot 
possibly attribute such “ fissures, like cracks in a broken pane of glass,” to 
either subsidence or elevation of such a mass of deep soil, which was never- 
theless imperceptible to the eye. Bishop Pocock, in the third book of his 
¢ Travels in Thrace and Greece,’ states that “‘ cracks were formed of six inches 
wide, by an earthquake which occurred at Zeitoun, but that it is situated on 
the south side or slope of a hill at the foot of a high mountain.” So that 
__ here there was a supported and an unsupported side to the embankment upon 
which the town stood. The fissures formed by the first shock of Calabria 
_ were greatly widened by subsequent ones; now this would not be the effect 
_ of direct action of the earth-wave, an elastic wave; but it would be just that 
᾿ς of slow separation, due to subsiding away, from any cause which left gravita- 
- tion to act; in fact, in a common slip upon a railway embankment may be 
_ seen in little, if the soil be favourable, all the phenomena recorded of earth- 
_ quake fissures in incoherent material. The first great fissures are produced 
_ when the slip occurs; others are formed in its mass after it has assumed a 
_ state of comparative repose. These, like the crevasses of a glacier, are all 
_ transverse to its general line of motion, just as they are in the earthquake 
| transverse to the line of motion of the shock, or may be; but every new vi- 
| bration, every passing train widens the mouths of these fissures, until the 
_ whole mass of the slip has gained its position of final repose. 
4 Again, some of the widest of these chasms, recofded as fissures, are of 
comparatively very small depth in relation to their width. Thus one at 
_ San Fili, the government Calabrian Commissioner, Grimaldi, found was half a 
mile long, two and a half feet in breadth at the surface, and only twenty- 
by five feet deep; and the deepest fissure I can find any record of, does not ex- 
ceed five hundred feet, and this does not seem to have been measured, and 
. is probably exaggerated. Now as the wave of elastic compression and ex- 
tension, or shock, traversed miles in depth of the earth’s crust at these places, 
le t is inconceivable that these fissures, if produced by its passage, should not 
| correspond with it in depth, or at least much more nearly than these com- 
| paratively shallow dimensions represent. 
_ Moreover, many of these fissures were crescent-shaped, as that near 
_ Soriano, and figured in the government account of the earthquake, and the 
_ Curve was extremely short and excentric; it is difficult to conceive such a form 
_ of fissure produced by fracture, i.e. by a shock of any sort or degree of vio- 
lence; while the excessively irregular figure of some others of the fissures, 
_ as that at Polistena (also figured), makes them quite as irresoluble on the 
fracture theory ; and indeed the gradual closing in of all these fissures by 
the slow subsidence of the soil, as noticed by the Government Commission 
