} 
ON SEISMOLOGICAL INVESTIGATION. 189 
railway cutting leading to the same, with the records of sudden displace- . 
ments and swinging of the instrument :— 
1895 Il. M 
August 30 7 20 P.M. Heavy blast. 
we 55 Peeoy uk Moderate blast. 
” ” 7 28 ” ” ” 
September 29 22 30 ,, In the cutting 
October 1 20-15; a 
Ee 2 19 3 i 33 double blast. 
3 3 22) NOs. » pit, heavy blast. 
” 4 23 5 ” ” ” 
Br 4 23:25) 55 a » 2 or 3 small blasts, 
be 8 19PZ0) 5 a8 », double. 
2 9 21 55 ” ” ” 
” 10 0 5 ” ” ” 
9 10 18 25 ” ” ” 
” 10 19 5 ” ” th 
» 10 23 20 ,, s9f eens 
Ae al br BF; Very heavy double blast. 
ye eat 21uBb. 3; In the pit. 
” 12 115 ” ” 
» 13 2015 ,, ” 
» 13 2215 ,, ” 
” 14 2 0 ” ” 
” 15 3 25 ” ” 
» 15 22 0 ,, ” 
” 16 2 0 ” ” 
” 16 20 45° ” ” 
” 17 0 5 ” ” 
Pa Huh 2155 ,, Very heavy. 
> as 21 40 
” ” 
The result of the comparison shows that in most instances no effect 
ean be traced to the explosions. In one or two instances, however, a 
slight blur from } to 1 mm. in width has been the result. 
The conclusion therefore is that the swingings recorded, which repre- 
sent sudden changes in the inclination of the ground, have not been the 
result of blasting. 
A few unusually heavy shots have, however, transmitted elastic vibra- 
tions as far as the instrument. These have caused the outer end of the 
boom to quiver but they have never produced a swing. 
The true amplitude of most of these isin all probability only a fraction 
of a millimetre and unless carefully looked for would hardly be visible in 
the photogram. 
A heavily laden cart passing at a distance of about 10 yards may 
produce a somewhat similar effect, but a light train at a distance of 150 
yards does not appear to produce any effect. 
Sudden Displacements and Earthquales recorded at Shide, 
By sudden displacements I mean movements like those shown in fig. 2. 
Usually, as here shown, they occur in groups, but now and then they occur 
singly. A similar appearance can be produced by gently pushing the 
pier carrying the instrument and then allowing the swinging boom to come 
to rest. Were they due to settlement in or beneath the pier, I should 
expect that they would be accompanied by permanent displacements which 
is seldom the case. A curious feature which now and then shows itself, 
and can be seen in fig. 2, is a permanent displacement of two or three 
