394 - DR. CHARLES DAVISON ON THE [ Aug. 1902, © 
nearly from Loch Ness to Inverness. There were two distinct 
slips in rapid succession, with continuous slight motion between 
them, the second being greater in amount and extending over 
an area which probably overlapped, even if it did not entirely 
include, that within which the first took place. 
After-shocks of 1901.—The immediate result of this dis- 
placement was a change of stress over a great extent of the 
fault-surface—a decrease, for the most part, near the centre of 
the principal focus, and an increase within and near its marginal 
regions. In places, the augmented stress produced secondary 
slips, each of which resulted in further changes of stress, and as 
a rule in decreasing slips, until the stresses were everywhere 
reduced below the maximum resistance capable of being offered 
to movement. 
The sequence of events is rendered clearer if, for the present, we 
disregard the very small slips (some of which may have been due 
to merely local variations of stress), and confine our attention to 
the six chief after-slips, three of which were of much greater 
importance than the rest, and affected several miles of the fault- 
surface. 
An interval of only 10 minutes separated the principal earthquake 
and its first successor. This was caused by a small slip (¢, p. 385) 
near the south-western margin of the principal focus. After 
21 hours, the chief after-slp (g, p. 385) occurred; its centre 
migrated about half a mile to the north-east, but, as the focus 
was several miles in length, its south-western margin extended 
some distance beyond that of the principal focus. The seat of 
action was then transferred to the other side of that focus, a long 
slip (h, p. 386) taking place after the lapse of about 5 hours ; 
its centre was approximately half a mile north-east of the principal 
centre, and its focus probably extended a little beyond the north- 
eastern margin of the principal focus. During the next 111 days 
there were no important movements; but at the end of that time 
a small slip (m, p. 388) occurred about 1 mile to the south-west 
of the principal centre, and close to Dochgarroch. This was followed, 
in 63 hours, by the third long after-slip (n, p. 388), the centre of 
which lay to the south-west of the principal focus, and the slip itself 
must have extended 2 or 3 miles beneath Loch Ness. Again, after 
a further lapse of 131 days, there was aslip (q, p. 390), about 2 miles 
long, in the immediate neighbourhood of Dochgarroch. 
Thus, of the six chief after-shocks, one originated within the 
region of the fault lying to the north-east of the principal centre, 
and the rest within that to the south-west. 
There remain eleven after-shocks recorded by more than one 
observer. Two of these had no connection with the boundary-fault; 
the epicentres of four are undetermined; of the others, the focus of 
one lay to the north-east, and the foci of four to the south-west, 
of the principal centre. 
Further light is thrown on the nature of the fault-movements 
‘Lotter hy 
