54 REPORT—1850. 
of the Neapolitan Academy, and also by Sir W. Hamilton, is alone sufficient 
to show that the elasticity of the formation in which they occurred was far 
too small to permit their formation by fracture. 
Of the extent of these subsidences at the time of the earthquake various 
instances have been recorded, such as the cylindrical lining of the well of the 
convent at Terra Nuova, being left projecting out of the soil like a tower, nine 
feet above the surface, and the lateral motion of the mass of soil in which it 
was dug, also evidenced by the whole well having got an inclined position 
from the vertical. That these subsidences produced often hollows of a cup 
form is not wonderful. 
In conclusion, I conceive the formation of all fissures, where effecting soft 
or incoherent formations, to be due to varieties of subsidence due to one 
form or another of landslips or land removal by water; that they may be 
and are produced in hard rock, and in buildings, &e., directly by the transit 
of the shock, I also conceive there is no doubt of, and this leads me next to 
a singular fact often recorded, viz. 
5th. At the moment the fissures open in the earth, fire and 
smoke (apparently) have been observed to issue. 
On this matter much new and exact observation would be most desirable. 
The narratives geuerally affirm that flame made its appearance momentarily 
at the mouth of the fissure, and that a volume of smoke, or some say dust, 
was vomited forth and hung for some time above the mouth. 
That some earthquakes have been observed from points situated so directly 
above and so close to the focus of veleanic action beneath, as to make all this 
quite possible in its most literal sense, cannot be doubted, when we call to 
mind the Volage’s chain cable having been made incandescent, and even 
partly melted, as she swung by it at anchor on the coast of South America ; 
or Captain Tilland’s narrative in the Philosophical Transactions for 1811, of 
the submarine volcano, which he actually saw rise, upon the surface of the 
sea, near the island of St. Michael’s, when laying to, within a few cables’ 
length of the spot. Within four hours after the first visible commotion, the 
summit of the crater was 20 feet high above water, and 400 or 500 diameter ; 
and before he left, it had raised itself to 80 yards in height. Volumes of 
steam were discharged, the sea was violently agitated as though boiling, light- 
ning-flashes were emitted from the clouds above, and water-spouts formed in 
various places around showed the violent disturbance of electric equilibrium. 
A continuous noise like musketry mingled with discharges of cannon stunned 
the ear, and the shocks of earthquake felt were sufficient to shake down part 
of a cliff upon which some observers stood. Many such records show how 
closely men may sometimes approach the “ Atri janua Ditis,” and live in the 
midst, as it were, of the smoke and fervent heat of the unknown regions 
within; but when the occurrence of flame and smoke is recorded of fissures 
in non-voleanic lands, and in territories suffering from earthquakes whose 
origin is manifestly far away, as in the Lisbon one for example, some different 
solution must be sought for. 
The following suggests itself as at least worthy of future investigation. 
The experiments of Becquerel and other electricians have shown, that when 
fracture in a solid takes place, a powerful electrical disturbance is the con- 
sequence. This will be great in proportion as the surface and mass fractured 
are themselves large. When therefore a fracture of a mile long and of many 
feet in depth is formed, whether by subsidation and slipping, or in any other 
way in soft material, and yet far more when one of those greater fractures in 
hard rock takes place, such as have been described when a whole mountain 
mass has been rent in two at a blow, the disturbance of electric equilibrium 
