“eA. Ste 
<3 
416 Geological Societ Ye 
Pliocene, the Sea of Marmora regained its former westerly extension 
to Gallipoli, and deposited the bed of Caspian shells on which that 
town 1s built. 
The lacustrine beach at Hora, 130 feet above sea-level, com- 
memorates., the last high-water mark of, the, Ponto-Caspian closed 
basin. The Egean. land, had, meanwhile -settled down, forming a 
large depressed. area, , probably ‘bounded. to: the- south: by the chain 
of the Northern. Cyclades,- and: the. Sarmatic beds dipped westward, 
reversing the. drainage .of: the, country south-west from Gallipoli. 
When the watershed of. a. river, occupying,the Dardanelles Valley was 
worn down tothe level ofthe Marmora, in: early Pleistocene times, 
the channel was‘rapidly. widened and, deepened to its present section 
by the outflow.of Pontic water... The. Mediterranean also passed the 
barrier ofthe Cyclades::during .the: Pleistocene Period, and when 
equilibrium was restored, the water. in; the Sea of Marmora stood 
somewhere. near its present level. There have been. various oscilla- 
tions since,. oft which the, positive changes-ofleyel are indicated by 
Pleistocene Mediterranean deposits ,at, Samothrake up, to 650 feet, 
and a raised beach at, Hora’at 400 feet, also by numerous shell- hanks 
and terraces, up, to 100.feet-above the present sea-level. There is, 
moreover, abundant evidence.of a rise to 1000 feet during or near 
the Glacial Period, by which‘ a red stony clay, formed at the expense 
of the surface-soil of a land-area, has been widely spread. 
2. ‘The Derby Earthquakes of March 24th and May 8rd, 1903.’ 
By Dr. Charles Davison, F.G.S. 
The undoubted earthquakes of this series were four in number. 
The first and strongest occurred on March 24th, 1903, at 1.30 P.m., 
and was felt over an area of about 12,000 square miles, its centre 
coinciding with the village of Kniveton, near Ashbourne. The 
shock consisted of two distinct parts, separated by an interval of 
about 3 seconds, which’ coalesced, however, within-a narrow recti- 
linear band running ‘centrally across the disturbed area at right 
angles to the longer axes of the isoseismal lines. The isacoustic 
lines (or lines of ‘equal sound-awdibility) are very elongated curves, 
distorted along the ‘rectilinear hand. The earthquake, it is con- 
cluded, was caused by simultaneous’slips within ‘two detached foci 
situated along a fault-surface running ‘from north 33° east to south 
30° west, hading to the north-west, and passing close to the village 
of Hognaston. - "The: strongest aftershock occurred on May 3rd, its 
focus lyi ing along the same fault, forthe’ most: part between the two 
foci of the. principal earthquake, but’) much nearer the surface. 
Observations of the principal earthquake were made in many of 
the mines ‘near’ ‘the epi¢entral district. “The sound, in: such cases, 
was a much more prominent feature than the shock; it appeared to 
travel through’ the: overlying strata, ‘anid ‘in-one pit: in‘-which ob- 
servations were made in. four seams at'different depths,-it was more 
distinctly audible: in the lower than in the.shallower.seams. 
The principal earthquake’ was registered by an Omori horizontal 
pendulum at Birmingham, by a Milne selsmograph at Bidston (near 
Birkenhead), and by a Wiechert pendulum at Gottingen (502 miles 
from the epicentre). The larger waves travelled with a velocity of 
2°9 kilometres per second. 
