68 
Proceedings of the Royal Society 
oil preventing the formation of small waves on their surface, must 
not he neglected, as it will reduce the bite or grip of the wind, 
and thereby reduce its action on the already fornied waves. 
Carrying out this process of reasoning, we see how the great 
waves of the ocean are increased and made dangerous by exactly the 
same process which we have seen in operation in smaller ones, 
only intensified and made more dangerous by the greater surface of 
the large waves, while the oil, by preventing the formation on their 
surface of smaller waves, hinders the development of dangerous 
crests. That oil has no other effect on the great waves of the sea is 
confirmed by the experiments made at Aberdeen. I am informed 
by Mr Smith, the harbour engineer, that there was no perceptible 
lowering of the waves after the water was covered with oil. Its 
action was simply to smooth over the waves and prevent them from 
cresting or breaking, an effect of great importance and value in 
making the entrance to the harbour safer during stormy weather. 
It will be observed, according to the explanation here offered, 
that oil has no power to calm waves ; it simply acts by preventing 
their formation and growth in certain ways. The resistance to ex- 
tension offered by an oily film will also have, no doubt, a slight 
effect in checking the up and down motion of the water, but the 
practical effect of this resistance must be very small and quite un- 
appreciable. 
It may be as well for us to note that the general question of the 
growth of waves has not been under consideration here, our atten- 
tion having been entirely confined to the effects of surface tension 
on their birth and development. 
Properly to understand the vast importance of so small a cause as 
the slight difference of tension produced by the oily film, we have 
only to remember that large waves have their genesis in tiny ripples, 
which by the cumulative action of the wind grow into large waves, 
and the oil, by preventing the formation of the ripple, strangles the 
wave in its birth. On the other hand, the perfectly balanced tension 
of the surface of clean water is as the “ letting out of waters,” as 
the thin edge of the wedge,” as the stone detached from the top 
of the mountain which brings along with it the irresistible avalanche. 
Prevent the beginning and the disastrous results are obviated. 
It might be thought that the difference between the surface ten- 
