Waves v4 
high the wave is, as long as its length remains about the same, 
its speed will remain constant. 
A small table which gives the speed of deep sea waves for 
different wave lengths might go something like this: 
Length in feet Velocity in knots 
SESE ea Re aeagelebnl ob RAT eee AR CNTY ial 
Ree args a ofan asci nt bos gh ae RR 2.4 
PER cece nea sil 8 a Gee te Me 3.8 
BTN ret 5s hs Alto ie a oc eh eaege RENG 4.5 
ee ere sl pS syntan s,s A ote eee ee 10.8 
[C1 BS gee ES ee ON ot ene aR ee rR ob gente 13.3 
ER ASEM SEE cl Sis titccg, She hy b ve oS Hatha Ree Ali ? 15.3 
OE SES ARO TSE RMA 3 LAC Soe ENT aE 18.7 
RNAS 2 ABM bE nate end wea sso ee aCe 21.6 
0 ALES ies A aii Aas Peri | Samoan ty Cas kaso 24.2 
LE i a eee er OIE Ea BO Lr) cere 38.2 
Ne eS, fee eee 48.4 
_ Where the water is shallow in proportion to the length of 
an ocean wave this simple relation breaks down. As waves 
move into shallow water their velocity decreases. 
Finally, when the water is too shallow, the lower particles 
of water are retarded by friction, the upper part becomes top- 
heavy and topples over to form breakers, or a “surf.” 
This change in the velocity of waves is to be seen on any 
sandy coast line. Far out at sea the waves follow one another 
in evenly spaced rows. As they approach the shallower water 
near the shore they slow down, crowd more closely together 
_and finally break. In this way waves adapt their shapes to fit 
the shore. © 
Most of these results and many others can be treated the- 
oretically. Hydrodynamics, that branch of theoretical physics 
which treats of the motion of fluid particles, is able to follow 
