6. REPORT—1858. 
The relative numbers as to horizontal direction :— 
Ss. to N. Nir RR RR Sih eri U5 to 
gs botnets oi iad ene Seber ce Aes ¢ 0-48 
1 A hale 1 ie eae rear (era abit» - 1:70 
oie uns We VVic sia cic die ecderevannt= ieee 0°73 
Ss. “el Fa abet ar an. Bet te, 
RV eee Win fae ste we tonne 5, © ere a 
5 ec eal tae ke AN Sborte -. 1°46 
WoW. 5 gamut eget S87 ob ain 
from which, by the preceding method, Perrey computes a mean horizontal 
direction of 
S. 39° 5! W. to N. 39° 5! E., 
which is about the line of direction of Loch Ness and of the Caledonian 
Canal. 
This is certainly, however, not the general or mean horizontal direction 
of British earthquakes, which appears to be one from south to north, veering 
more or less to the east or west, but having on the whole a direction passing 
through the probable focus of the Lisbon earthquakes and of the Canary 
Islands. I am not aware that any attempt has been made to ascertain 
the angle of emergence of the wave of shock for any British station, except 
indirectly by myself, in my “ Memoir on the British Earthquake of November 
1852” (Trans. Roy. Irish Acad. vol. xxii. part 1) at Dublin, which was from 
25° to 30° inclined to the horizon; and assuming the origin to have been 
even somewhere between Great Britain and Lisbon, the depth of focus must 
have been very great; that earthquake extended over the greater portion 
of the British Islands, the maximum disturbance on the surface being about 
Shropshire. 
Mr. David Milne, in one of a series of very able papers on British earth- 
quakes in the ‘Edinburgh Philosophical Journal,’ vols. xxxi.xxxvi., which 
I regret not having noticed in my Second Report as prominently as they 
deserve, expresses his conviction (as it appears to me, however, from very 
insufficient grounds) that all British earthquakes have had an origin of 
disturbance immediately beneath Great Britain, and not at some distant 
point beyond, his chief reasons being, 1, that with few exceptions they 
affected only certain portions of the island; 2, that there was in all the 
districts affected some spot where the concussion and attendant noise were 
greater than anywhere else, and that they diminished with their distance 
from this spot ; 3, that the shock and the noise moved simultaneously from 
this spot. 
A reference to the Catalogue will show that these are by no means the 
general prevailing facts: and if they had been so, they do not prove the 
point, for reasons to be gathered from the Second Report. In the absence 
of any knowledge of the angle of emergence, it is a very incomplete state- 
ment of fact when Milne says, that “out of 110 shocks recorded in England, 
31 originated in Wales, 31 along. the south coast of England, 14 on the 
borders of Yorkshire and Derbyshire, and 5 or 6 in Cumberland.” “ These 
facts,” he adds, “seem to show that the seat of action cannot be very far 
down in the earth’s interior.” Locally variable surface-disturbance, and even 
none at certain localities, within large areas exposed to seismic action, are 
amongst the most common phenomena of observed earthquakes even of the 
greatest extent and intensity, and arise, amongst other reasons, from the 
heterogeneous and dislocated materials of the earth’s crust perturbing the 
