748 REPORT—1899, : 
beaches from the south along the coast from Deal to Ramsgate, and on the north 
of Kent their drifting from Margate to Whitstable. 
The changes in the direction of the mouth of ‘the Stour, and the resultant 
action of the same in the rapid erosion of the cliffs at Pegwell Bay ; illustrating 
these changes with sketches taken at different times during the last forty years, 
and with reference to the Ordnance maps. The rate of erosion of the chalk of 
Thanet is herein discussed, and also the permanence of certain submarine shoals 
and sand and gravel banks in the coast-line near Ramsgata. 
The effects of erosion in the jointing and faulting of the Thanet Cliff and fall 
of the cliff and its removal by natural and artificial causes. 
Especial results of the abnormal high tide of November 29, 1897, with the 
north-east gale that accompanied it. 
The Whitstable bank, known as the ‘Street,’ is described, and the change in 
its character during the last ten years recorded. 
Finally, the author discusses the probable oscillations in the level of the land 
and the total result, being subsidences since the Roman occupation of Britain. 
6. Preliminary Report on Observations of Coast Hrosion by the 
Coastguard. 
7. On Photographs of Wave Phenomena. 
By Vaueuan Cornisu, ISc. (Vict.), F.R.GS., FCS. 
Part Il— What is a Wave? 
The connotation of the word ‘ wave,’ which is becoming customary from the 
special aspects of waves most studied in physics, is that of transmission of energy 
in a pulse-like manner, attention being concentrated on a process and diverted 
from the thing produced. This is well enough eg. in the physical study of light, 
where the structures produced are obliterated almost as soon as formed; but it is 
not the right point of view in geology, where the structure frequently outlasts the 
process, and the process of production is by no means always a pulse-like trans- 
mission of energy. The primary and principal meaning of ‘wave’ (noun) in our 
language’ is properly associated with (1) up and down motion, (2) with a 
systematically corrugated surface, an onward rushing mound of water; the notion 
of pulse transmission comes in but slightly. 
The most fruitful source of the waves which constitute geological structures 
is the relative motion of two bodies which yield viscously at their common sur- 
face. An undulating interface is an almost invariable result of such movements, 
whether of a lighter air over a heavier, giving clouds in parallel bars, or sometimes 
a mackerel sky ; or of atmosphere and non-rigid parts of the lithosphere, giving 
blown-sand ripples, sand dunes, or waves of drifted snow; or hydrosphere and 
non-rigid parts of lithosphere, giving ripple-mark of the seashore, tidal ripple- 
mark of estuaries, sand banks, ripple-drift, ‘ sand reefs,’ &c.; or between parts of 
the lithosphere, when the relative movement is slow enough to allow them to 
behave viscously. In this case of slow wave formation, pulse-transmission may 
be present, but difficult to observe directly. Moreover, the structures are often 
ia in the ‘fossil’ state, e.g. rock-folds, when no longer part of the living 
rock. 
Sudden interruption of such slow wave-making (e.g. fold passing into fault, the 
wave ‘ breaking’) brings out elastic effects, and waves such as those of earthquake 
shock become possible, in which the pulse-transmission-of-energy-aspect of waves 
‘See Johnson’s Dictionary of the English Language (Latham, 1870); W. W. 
Skeat, An Etymological Dictionary of the English Language, 1898; J. Bosworth, A 
Dictionary of the Anglo-Saxon Language, 1838, and as edited by A. N. Toller, 1892 ; 
and Cruden’s Concordance of the Old and New Testament. 
