]Vni. IVIALLET OX THE TEAXSIT-VELOCITT OE EAETHQTJAKE WAVES. 679 
a view to the interesting question of the relation between the theoretic velocity of 
transmission, if the rock were all solid and homogeneous ^V= \/22 g being that 
modulus^ , and the actual velocity found by the preceding experiments. 
In their direct relation to Seismology the interest of the foregoing results is not as 
great as when some years since I commenced these experiments. At that period no 
knowledge whatever existed as to the relation that subsists in nature between the 
velocity of transit and the velocity of the particles in wave-movement in actual earth- 
quakes. Geological obser\’ers, in fact, did not appear to be aware of any such physical 
distinction ; and those who were so, presumed that the velocity of the particles was like 
that of transit, extremely great, and that some simple relation would probably be found 
between them. 
The first determinations of velocity of the particles in wave-movement that have ever 
been made, namely, those by myself of the great Neapolitan Earthquake of 1857, have 
dissipated this notion, however, and proved that the velocity of the particles in even 
the greatest shocks, is extremely small, not exceeding 20 feet per second in very great 
earthquakes, and probably never haAlng reached 80 feet per second in any shock that 
has occurred in history. No simple relation appears as yet between the transit-velocity 
and that of the particles ; and, however interesting and important both to general physics 
and to Seismology may be further determinations with exactness of the former, it is to 
the observ ation and measurement of the latter, by the methods pointed out in the Eeport 
upon the Neapolitan Earthquake*, and there employed, that we must look as instru- 
ments of futui'e seismological research. 
* Xow in the press. CnAPiiAX and Hall, London : 2 vols. 8vo. 
4 z 
MDCCCLXI, 
