t the phenomena
admitted by reference to any general mechanical or physical causes. In
1850 my first "Report upon the Facts of Earthquakes," called for by the
British Association in 1847, was read and published in the Reports of
that body for that year. In this, for the first time, the many recorded
phenomena of Earthquakes are classified, and the important division of
the phenomena into primary and secondary effects of the shock was
established. Several facts or phenomena, previously held as marvellous
or inexplicable, were either, on sufficient grounds, rejected, or were,
for the first time, shown susceptible of explanation. Amongst the more
noticeable results were the pointing out that fissures and fractures of
rock or of incoherent formations were but secondary effects, and, in the
latter, were, in fact, generally of the nature of inceptive landslips.
This last was not accepted, I believe, by geologists at the time; but
the correctness of the views then propounded as to earth fissures--the
nature of the spouting from them of water or mud--the appearances taken
for smoke issuing from them, etc.--have since been fully confirmed,
first, by my own observations upon the effects of the Great Neapolitan
Earthquake of 1857, and more lately by those of Dr. Oldham upon the
Earthquake of Cachar (India), where he was enabled to observe fissures
of immense magnitude, the nature of the production of which he has well
described and explained in the "Proceedings, Geological Society, London,
1872."

The relations between meteorological phenomena proper and Earthquakes
have always been a subject of popular belief and superstition.

This was here carefully discussed, and with the result of disproving any
connection, or, if any, but of an indirect nature. I also, to some
extent, towards the end of this Report, discussed the question of the
possible nature of the _impulse itself_ which originates the shock; I
showed that it must be of the nature of a blow, and ventured to offer
_conjecturally_ five possible causes of the impulse:

1. Sudden fractures of rock, resulting from the steady and slow
increase of elevatory pressure.

2. Sudden evolution (under special conditions) of steam.

3. Sudden condensation of steam, also under special conditions.

4. Sudden dislocations in the rocky crust of the earth, through
pressure acting in any direction.

5. Occasionally through the recoil due to explosive