TRANSACTIONS OF SECTION C. 825 
appear to have been very fully discussed ; and he points out that it seems to have 
been assumed that there is no alternative between the two hypotheses, either that 
there has been a general lowering of the ocean all the world over, or that the 
land has been repeatedly moved upward or downward. He states that the alter- 
native doctrine, inferable from a logical analysis of astronomical phenomena 
bearing upon the subject, does not appear to have been seriously considered, and 
he mentions that some actual evidences are available, showing that in relation to 
the land the surface-level of the sea has, within comparatively recent historic 
times, hecome altered in some localities without any simultaneous uprising or 
dilatation of the solid land. He proceeds to show that the aiteration in the shore- 
line of the coast, whereby the old sea-ports of Winckelsea and Rye have become 
inland towns, has been accompanied by a gradually progressive reduction in the 
depth of the water off that coast; that the surface-contour of the land up the 
valleys debouching on to the flat or level between those towns plainly indicates 
that when the sea flowed in and out of those valleys, as it did prior to the time 
of its receding from the old coast line, now some distance inland, and extending 
from Winchelsea to Rye, its surface-level in that part of the English Channel was 
higher than it now is even at the times of highest high tides; that the absolutely 
undisturbed structure of the Hastings sand-deposit—of which that inland district 
consists—defies the supposition that the ‘change of level’ between the land and 
sea surfaces in that neighbourhood has arisen from the upheaval of the land, and 
further, that certain ancient documents now existing in the Town Hall of Rye-— 
among others, a charter of King Richard I. (in 1194) and a document of Kine 
Henry III.’s time (1248)—plainly show that prior to those dates the sea had sur- 
rounded the town of Rye, and that by reason of that town being no longer insu- 
lated it was more open to the attack of enemies, rendering necessary the repair 
of its walls of defence. The author also points out that certain circumstances, 
incidentally mentioned by Leland, Jeake, and other old writers, afford further 
historic evidence to the same effect. 
5. Notes on Volcanic Eruptions. By THomas Hart, F.G.S. 
It seems to be an undoubted fact that water coming into contact with highly- 
heated rock is one of the most important requisites to produce and sustain a volcanic 
eruption. 
The difficulty has been to explain how the passage of water in such considerable 
quantities is brought about. 
The author thinks that we must look to some other explanation than a supply 
from ordinary percolation alone, and refers to the active volcanoes of the world 
being in close proximity to coast lines or in land areas surrounded by the sea, also 
in a more special degree in voleanic island groups. 
In his account of the great eruption of Vesuvius in 4.p.79 Pliny the Younger 
says: ‘There had been noticed many days before a trembling of the earth, but 
that night it was so violent that one thought that everything was being not merely 
moyed, but absolutely overturned.’ 
The author suggests that the principle of the ‘ self-acting injector,’ now generally 
used for supplying steam-engine boilers with water, comes into play during violent 
paroxysmal outbursts of voleanic activity, and is assisted by the d/ast afterwards 
produced by the conversion of water into steam. 
In the construction of these injectors the elastic force of the steam in the boiler 
is utilised, not only to force water into the boiler itself, but when required to lift 
‘it ten to twenty feet in addition as in a pump. 
Therefore, applying this principle to the great eruption of Vesuvius in a.p. 79, 
the impetuosity of the current from below would carry water from the Bay of 
Naples along with it through the fissures produced by the preceding earthquake. 
The same principle will apply to all volcanic eruptions, the water being 
‘supplied either by percolation, the sea, or both combined. 
1890. 3 
