108 
PHYSICAL AND MATHEMATICAL SECTION. 
April 2nd, 1863. 
Joseph Baxendell, F.R.A.S., President of the Section, in 
the Chair. 
A Paper was read entitled “Notes of Observations of the 
Speed and Order of Succession in Magnitude of Waves 
observed in Gales of Wind off the Cape of Good Hope,” by 
Mr. Thomas Heelis, F.R.A.S. 
The highest waves measured were about 35 feet in height 
from the trough, no broken crests having been measured. 
Their speed varied (the force of the wind being 8 according 
to the Board of Trade scale, and equal to weather in which 
a ship on a wind can just carry treble-reefed topsails) from 
twenty to twenty-three miles per hour, the breadth of trough 
being 300 to 350 feet. The observations show that usually 
the succession of magnitudes (or heights) returns in series of 
twelve waves, the first and second of each series being very 
large, the sixth or seventh being also large but inferior in 
magnitude to the first and second, and the intermediate ones 
being small. The observations show that waves are limited 
in length, measured along their bases, the crest being 
apparently at the middle point of the base, and the length 
varying with thS altitude of the crest, and that the order of 
succession of magnitudes depends upon their being arranged 
so that the crest of one wave follows on the same line as the 
lower flanks of a preceding wave. The speeds also of waves 
appear to vary, so that a following wave often coalesces with 
and is increased in size by absorbing one immediately 
preceding. When a wave is first formed it is small, and 
increases in size in its progress, until the crest topples over in 
foam, after which the height decreases rapidly, and there 
seems reason for thinking that if ordinates were drawn so as 
to represent the height of any wave at different periods of its 
existence, its height would be found to coincide with Mr. 
