399 0.8. Lyman’s new form of Wave apparatus. 
18. The fact of sensibly still water at half a wave’s length 
below the surface. This is exhibited in the absence of lateral 
motion at the lower extremities of the upright wires, and is a 
necessary result of the law of diminution of orbits with depth, 
as given above (13). 
€ varying strain, in wave action, on floating vein 
This is seen in the varying angle made by the upright wir 
with the upper transverse wire; the latter shows the position 
of a raft, for example, lying on the wave surface ; the for- 
mer, that of a a long, thin body, as a board, floating end down; 
hence, the varying relative direction of the wires shows the 
“ness, a few formule are added, expressing other relations 
among wave phenomena, not so directly exhibited by the instru- 
ment, but important to be presented in connection with it. 
Putting V for the velocity of propagation of a wave, and the 
other symbols as before, the length of the wave is 
2 
I= %R =o Pe wets 
its period nV ee sfich 
the cad of a os in its orbit, oe at ihe crest of the wave, 
fs ce av —~ seat 3 r ie i i 
the ast of prea of the wave 
to W 
ppli » , and which the apparatus ittustrates, i is the wave 
sore ep ~ ate = or water a wave’s length, at least, in depth. In 
Water, the Ti no ees sy but he or nF 
