406 B. K. Emerson on Seebach’s Earthquake in Germany. 
would seem that this source of information had been very 
nearly exhausted, and that resort must be had to a purely 
physical treatment of the subject. The Earthquake Reports of 
Robert Mallet* had done much to render this possible, es- 
pecially by perfecting the ere by the beautiful mathe- 
matical determination of t e of greatest intensity, the the- 
orem for finding the ares froin, the time of shock at three 
core at Holyhead, North Wales.{ It was eminently fitting 
wl wave aNigecn th of the = centrum,” or region 
ej the position of the “ epicentrum” 
now of no aac attempts to determine any of these ele- 
ments, except the early, very imperfect ones, by Milne, of the 
would intersect on the earth’s surface at the “ epicentrum,” or 
ge directly over the focus, the inclination of these two sets 
to each other giving the angle of emersion for each 
place of observation. Further, the angle of emersion thus 
own, the velocity of vibration of the wave was obtained by 
calculation from the distance to which bodies of known weight 
* Brit. Assoc. Rep., 1850, 51 oe Set 58. 
{Aceon Rep. o of Earthquake P omena, _ Brit. Assoc., 1851. 
Account of ——— made oe a Holyhead to ascertain the transit velocity of 
to earthquake waves through local rock formations, Phil. Trans., 
1861, p. 655. 
Ed. Phil. Jour., vo! ] This Jour., rs xxv, p. 146. 
Das Erdbeben von en —e 1846, im Rheingebiet on Dr. Jakob Néggerath. 
ee Oe ae Erdbeben am 15 Jan. 1858, J. F. Schmidt, As- 
tronom. Athen.; Mit. d. K-k. Geograph. Gesell., zu Wien, 1858. 
: gre gy Neapolitan Earthquake, or the Principles of Observational Seis- 
OB a & 
