F. W. Oliver. 
So 
a more or less prolonged phase of hook-formation—the phase of 
maturity. In other words, the spit grows at first under the organising 
influence of the littoral current, but sooner or later its point will 
extend to a region where it becomes subject to a conflicting current, 
so that hook-formation supervenes. 
This conflicting current will in most cases be the tidal current 
which fills the area on the lee side of the spit, and its action in 
determining hook-formation is automatic—the inevitable con¬ 
sequence of the increasing scour to which the point of a lengthening 
spit becomes subject. In illustration we may take the case of a spit 
making an angle of 45 n with the shore-line. Let perpendiculars be 
erected on the spit at intervals of a mile and produced till they 
intersect the shore-line. The area enclosed by the perpendicular 
at the 1 mile station will be -5 square miles, at the 2 mile station 
2 square miles, at the 4 mile station 8 square miles, at the 6 mile 
station 18 square miles, and so on. In other words the areas to be 
filled by the tide mount as the squares of the distances. Thus the 
volume of water that will have to pass behind a 10 mile spit will be 
one hundred times as great as that behind a 1 mile spit, and this 
of course in the same period of time. If the whole of this water 
were to run in a channel whose sectional area remained constant, 
the rate of flow in the former case should be one hundred times as 
fast as in the latter. Allowance has to be made however for pro¬ 
gressive shallowing by silting up behind the spit (and consequent 
relative diminution of the volume of water needed to fill it), and also 
for the widening of the aperture as the point of the spit gets further 
from the land. Though it is impossible to attach concrete values 
to such factors as these, the general conclusion may be drawn with 
little risk of error that as a spit lengthens it becomes subject to 
increasing tidal scour, which, when correlated with heavy on-shore 
gales, will lead to the transfer of material and the production of a 
landward hook. That hooks are directed towards the land and not 
towards the sea—notwithstanding the equivalence between the tidal 
currents of ebb and flow—depends on the non-production of waves 
when the wind blows off-shore. 
Thus we see that as a spit grows in length it will become more 
and more susceptible to the hook-forming agencies which will also, 
automatically, arrest its power of growth in length. 
There is, of course, another factor which must work in the same 
sense, viz., the attrition factor. If the supplies of drifting shingle 
be assumed to remain constant, as the spit grows the losses due to 
