VI. 
WAVE OBSERVING. 
By CoMMANDER WILSON-BaRKER, R.N.R., F.R.S.E. 
A FEW rules on the observation of waves, their height, speed and 
movement, may not be out of place in this volume. The subject is 
deeply interesting, and much correct and valuable information may be 
easily obtained by those who will take the trouble to be accurate in 
their method of working. The length of a wave is its measurement 
from hollow to hollow, or from crest to crest; its height is the 
vertical distance from crest to hollow ; a wave’s period is the number 
of seconds it takes to travel a distance equal to its length; and its 
velocity is the speed of advance of the wave crest (counted in feet) 
per second. To ensure correct reckoning, two observers should 
operate : 
A, to watch the waves ; 
B, to write down the time. 
Thus, A takes his place in that part of the ship most convenient 
for his purpose, presumably on the bridge; he fixes on a particular 
point for observation and sets to work. He first notes the direction 
and speed of the ship, the direction * and force of the wind, and 
the direction of the sea. He then tells B to look out, and each 
time a wave reaches his point of observation, sings out, “Stop!” 
B promptly writes down the time. 
The speed of a wave is ascertained by noting the time it takes to 
travel the length of the ship. To find the height of a wave above 
water line, the observer should mount the rigging, or other con- 
venient spot, until high enough to see the horizon over the top of the 
crest. Thus, if he mount ten feet above the deck (which is ten feet 
above water line), and can then see a wave crest level with the 
horizon, the height of that wave is twenty feet. This observation 
must be taken at a moment when the ship is on an even keel (upright). 
Three or four different sets of about thirty observations each 
* Best found by observing the curl on the waves. 
