234 REPORT—1899. 
are not considered disturbances, but much smaller oscillations than these 
can easily be detected in the curves. In order to avoid any arbitration 
as to what disturbance should be singled out for the purpose of comparing 
~with the list of earthquakes, in cases where the curves appeared to be 
generally disturbed, or where more than ene disturbance occurred, or 
where several disturbances presented different characteristics, Mr. Barrachi 
has put down in the following notes all the distinctive features of the 
curves occurring within several hours, in some cases 10 or 12 hours, before 
and after the times specified in the earthquake register, noting also every 
appreciable oscillation, however small, so that those who make com- 
parisons may discriminate for themselves. All times in the list are 
indicated as Melbourne Mean Astronomical Time, the day commencing 
at Melbourne noon, the hours being reckoned from 0 to 24. By 
amplitude is meant the whole range of displacement. Period means 
the time taken for the double swing. When there is a movement from 
the neutral line upwards and back to the same, followed some time later 
by a movement downwards and back to the same, the latter is said to be 
in the ‘opposite phase’ to the former. As these two movements may be 
independent of each other it will be recognised that the term ‘ opposite 
phase’ is one of convenience. ‘Superimposed waves’ means that there 
are small waves which appear as regular or irregular, large or small, 
serrations on the trace of larger waves. 
The earthquake list referred to by the numbers, dates, and times in the 
first three columns is given in the ‘ British Association Report’ for 1898, 
. 227, 
Melbourne astronomical time is 9h. 39m. 53°8s. in advance of 
Greenwich. 
1889. 
M.M.A.T 
Ha. OM, 
4 | Aprills. a Wabi IL Minute wave from lh. 40m. to lh. 45m., amp. under 30” 
followed by still minuter waves from 2h. 0m. to 2h. 20m. 
2) July1l. 20 2 | Minute oscillations commenced 13h. 45m. to 14h. 5m., 
amp. under 20", larger oscillations of longer period, amp. 
above 2’, from 14h. 15m. to 17h. 45m., maximum amp. 
at 17h. 20m. about 3’. 
5) | peace ws) 13 10 ,| Slightly disturbed from 15h. 40m. to 18h. One oscillation 
of long period from 15h. 0m. to 15h. 22m., amp. above 2’, 
followed by minute waves of shorter period. Com- 
mencement (more accurately), probably 15h. 35m. No 
4 aay CER 15 40 other disturbance before that hour appears on this curve. 
5 | Aug.25 . 17 17 | Decided disturbance commencing 9h. 50m., with one oscilla- 
tion, amp. 33’, period 40m., followed by another wave, 
amp. 53’, time of max. amp. 11h. 5m., then followed by 
less marked and irregular oscillations for 6h., gradually 
| becoming normal shortly after. 
1891. 
| Curve disturbed from 7h. 5m. max., disturbances at 7h. 5m., 
| with a large wave amp. 6’, period 33m., and at 14h. 40m., 
| with a large wave in opposite direction, amp. 7’, period 
47m., followed by minute waves of very short period till 22h. 
BOct. 275.) 719 a8 
13892. 
Slight, but well marked disturbance, commenced 8h. 30m. 
ending 9h. 35m., consisting of two waves, amp. from 
4' to 5’. 
7 ) Mar. 16. 
