106 
EARTHQUAKES IN AUSTRALASIA,.—III. 
BY GEORGE HOGBEN, M. A TIMARU, NEW ZEALAND. 
21) 
REFERENCE has already been made to the first report 
(1891) of the Seismological Committee of the A.A.A.S. 
(see Sczence, vol. XXI., p. 344), which, with a paper by 
the present writer, included summaries of all the known 
records of earthquakes in New Zealand to the end of the 
year 1890. The second and third reports of the same 
committee (1892 and 1893) have continued that .work to 
the close of last year, and have added thereto similar sum- 
maries for New South Wales, Victoria, South Australia 
and the New Hebrides. ‘The committee have also had 
placed at their disposal the observations (made under the 
direction of the late Captain Shortt, R.N., meteorological 
observer at Hobart, Tasmania) of a most remarkable 
series of shocks that occurred in Tasmania during the 
years 1883-1886. The large number of these shocks 
(2540) made it undesirable, if not impossible, to publish, 
even ina brief form, the details of each earthquake; but 
the chief results have been analyzed in two papers read 
before the last meeting of the Australasian Association; 
of these mention will be made below. ‘The most interest- 
ing part of the last report (1893) is perhaps that contain- 
ing the records from the New Hebrides. ‘These consist 
of careful notes made by a missionary—the Rev. W. 
Gray—stationed at the Island of Tanna, and form the 
first fruit of our work inthe Pacific, as distinguished from 
that on the continent of Australia and in New Zealand. 
Tanna contains one of the three active volcanoes in the 
group, and eruptions are frequent; nevertheless, though 
the volcanic and seismic phenomena are probably not un- 
connected, a large number of the earthquakes do not seem 
to have the characteristics of those commonly classed as 
volcanic. One feature of the earthquakes of the New 
Hebrides is the remarkable rise of land that has on 
several occasions been observed to follow the shocks. 
Darwin alludes, it may be remembered, to the recent ele- 
vation of these islands (‘‘ Coral Islands,’’chap. vi.) ; it is in- 
teresting to notice that they are still rising, and by 
no meansataslowrate. In Steel’s ‘“ New Hebrides ” it is 
stated that elevations of land took place after the earth- 
quakes of Jan. ro, 1878, and Feb. r4, 1878, of twenty 
and twelve feet respectively; and further that ‘‘rocks which 
were formerly covered with seven or eight fathoms of 
water are now above high-water mark ” (Steel, ‘‘ New Heb- 
rides,” p. 189). ‘The rise in the last two cases appears to 
have been local in nature, at least as regards the magni- 
tude of the elevation. Here and there in books and 
papers upon the New Hebrides allusions less definite in 
character may be found to elevations of land in other 
islands, especially Aneityum. The Rev. W. Gray has 
supplied, in a letter accompanying his observations of the 
New Hebrides earthquakes, very definite details of eleva- 
tions of land following two earthquakes, in 1888, which I 
believe have not before been placed on record, though they 
are quite as striking as the historical case noted by Darwin as 
having occurred on the coast of South America in 1835. 
On April 20, 1888, an upheaval took place at Tanna, 
exposing a new beach 58 yards in width. Mr. Gray says, 
“On examining this part I walked over ground dry-shod 
where a year ago I sailed in a boat and where at one time 
there was thirty feet of water.” 
The earthquake of June 24, in the same year, extended 
the beach another 97 yards seawards, the total width of 
new beach being 155 yards. Unfortunately Mr. Gray 
does not give the vertical height through which the coast 
was raised; but his description seems to imply a total 
upheaval for the two earthquakes of 4o feet at least. Near 
the middle of the beach last formed he marks a spot thus: 
‘At this spot our mission-vessel lost an anchor 
SCIENCE 
Vol. XXIII. No. 577 
more than ten years ago. It was brought up now.” 
The New Hebrides are cut off from the Loyalty Islands 
and New Caledonia by a narrow but deep trough in the 
ocean bed; yet some of the earth movements in these 
groups seem to correspond with one another. In the 
absence of more exact information it is premature even to 
hazard a conjecture; but should a sufficient correspondence 
be established, it wouldseem to show, (1) a deep-seated 
cause for the disturbances, (2) a general movement of 
that part of the floor of the Pacific Ocean. We hope to 
get evidence on these points shortly. 
Two papers of mine read before Section A of the 
A.A.A.S. (Sept., 1893) dealt, the one with ‘‘Earthquake- 
Intensity in Australasia,’ the other with the ‘‘ Tasmanian 
Earthquake of January, 1892." The former was suggested 
by a paper by Dr. Edward S. Holden, Director of the 
Lick Observatory, entitled ‘‘ Earthquake-Intensity in 
San Francisco” (American Journal of Science, June, 1888). 
Dr. Holden gave therein the equivalents of the degrees 
of intensity of earthquake-shocks on the Rossi-Forel scale, 
in terms of the acceleration due to the velocity of the 
shock itself, expressed in millimetres per second; he then 
applied his table to form an estimate of the intensity of 
the shocks felt in San Francisco. I have done the same: 
for the Australasian Colonies. For New Zealand we have 
for the years 1848-1892 the records of 926 earthquakes; 
but in the earliest years only the severest shocks were 
recorded, and until December, 1889, when the present 
system of observation through the officers of the Telegraph 
Department was begun, most of the shocks of intensity 
I. to III. on the R.-F. scale were probably neglected. Now 
comparatively few pass unnoticed; I have therefore taken 
the records for the three years, 1890-1892, only. ‘The 
number of shocks is 198, and the mean average intensity 
per shock, as feltin New Zealand, is 72 m.m. per second, 
that is to say, between III. and IV. on the Rossi-Forel 
scale, or sufficient to make pictures move a little and to 
cause some doors and windows torattle slightly. 
For New South Wales (12 years) and Victoria (8 years) 
the average intensity is about IV. ; but the records evidently 
omit nearly all the slighter shocks, and so this estimate 
is undoubtedly much too high. In South Australia, where 
somewhat fuller records were kept, the average intensity 
(10 years) is only a little over III. on the R.-F. scale. 
The study of the remarkable series of earthquakes in Vas- 
mania and southeast Australia, between April, 1883, and 
December, 1886, in conjunction with the determination of 
the origins of the principal shocks, opens up several 
questions of great importance, which it would take too 
long to discuss here. The total number of shocks for 
the 45 months was 2540, an average of 56.4 shocks per 
month, which would be sufficiently startling were it 
not that the average intensity of shock was only 
between III. and1IV. (71 m.m. on the absolute scale). One 
month, October, 1883, enjoys the questionable distinction 
of having 231 shocks recorded against it, that is, seven or 
eight shocks a day; and November of the same year is 
not far behind. A second maximum of intensity was 
reached in August, 1884; and then a very gradual decline 
took place for nearly 21/2 years, the shocks slowly dying 
away at the end of 1886. The only considerable earth- 
quake since then is that of January 27, 1892, felt all 
over Tasmania and in southeast Australia, for which the 
data were sufficient to determine the origin very nearly. 
It is situated below the deep trough of the Tasman Sea, 
about 353 miles east of Launceston and 365 miles from 
Hobart. ‘The chief shocks of 1883-1886 may be referred 
with more or less probability to the same neighborhood; 
but many of the smaller shocks were more local. For 3 
or 4 years a re-adjustment of the earth’s crust was going 
on steadily; the larger shocks were perhaps merely in- 
