Vol.58.] THE CARLISLE EARTHQUAKES OF JULY 1901. 373 
there were evidently two maxima of intensity, with intervening 
weaker motion and fainter sound. At no great distance from the 
longer axis, these intervening vibrations became imperceptible to 
many observers, and the shock consisted of two detached series of 
vibrations, separated by an interval of about 3 seconds’ duration. 
This double series was perceived over an area the outer boundary of 
which coincides nearly with the boundary of the disturbed area of the 
third shock (indicated by the outer dotted line on the map), except 
that it is less elongated in form, extending 2 or 3 miles beyond it 
towards the east, and falling short of it by about the same distance 
towards the north and south. Towards the boundary of the dis- 
turbed area, the shock consisted once more of a single series, the 
weaker part of the shock apparently becoming imperceptible. 
The continuity of the shock over a band extending from Carlisle 
to Coniston, implies a corresponding continuity in the focus. The 
disposition of the isoseismal lines, however, in conjunction with the 
observations on the shock, shows that within the focus there were 
two regions of initial maximum intensity. The principal 
region must have been near the centre of the isoseismal 5; the 
other appears to have been in the neighbourhood of Grasmere, for, 
in this district, there is evidence of a slight increase in the intensity 
of the shock. The records of the order of relative intensity of the 
two maxima or series are few in number; but it is probable that 
the slipping began at the northern end of the focus, and took place 
rapidly throughout its whole extent. | 
The average of forty-five estimates of the duration of the shock 
is 7:2 seconds, or, excluding eight estimates varying from 124 to 
30 seconds, the average is 4°1 seconds. 
Sound-phenomena.—tThe sound was heard all over the dis- 
turbed area, and by 90 per cent. of the observers. The percentage 
of audibility varies very slightly in different parts. Within the dis- 
turbed area of the third shock (the boundary of which is approximately 
an isoseismal of the first shock), the percentage is 90: outside it, it 
is 893: an uniformity which is probably due to the great depth of 
the focus. It is evident, however, from the descriptions, that the 
sound was by no means of uniform intensity. Comparisons in some 
places to very heavy waggons passing, to the crash of a steam- 
roller against the house, to dreadful explosions, etc., and in others 
to distant thunder (a very common expression), wind, or a distant 
explosion, show that there were two regions of maximum intensity, 
the boundaries of which are difficult to define. One of them lies 
within the isoseismal 5; the other includes such places as Amble- 
side, Coniston, Grasmere, Hawkshead, Rydal, and Wythburn, at 
several of which the intensity of the shock was greater than in the 
surroundizg district. 
The sound was compared to passing waggons (a passing motor- 
car appearing for the first time in such references) in 33 per cent. 
of the records, to thunder in 35 per cent., wind in 6, loads of stones 
Q.3.G.8. No. 231. 2D 
