66 THE TROCHOIDED PLANE. 
r may be abstracted from the swell of the ocean by 
means of the trochoided plane, thus :—Take a flat float, and rigidly 
connect a plane at some distance below parallel to the float, and it 
will be found that the plane and float alternately pull each other 
in the direction of propagation of the waves, the result being that 
the apparatus ——— through the water faster than a float 
without the plane at 
If the plane is fixed vertically, or at right angles with the float, 
the resultant is in a direction contrary to that in which the waves 
are movin 
Again, # two floats are connected by linkwork end to end, and 
separated by a distance equal to half a wave, the neha move- 
seaway, the length of the hawser should be such that both vessels 
are as near as possible to the crests of waves at the same time ; if 
there is a cross sea, this is impossible ; if the sea is at all regular, 
attention to this, whether by accident or design, saves many @ 
savage jerk to the tow-line; the distances, } wave, 14 waves, 24 
waves, are obviously those to be most avoided. 
I will now draw your attention to the motion of living organ- 
isms, and how their movements seem to me to have a common 
origin, and that the trochoided plane is the mechanical power 
trochoi 
that if they are rotated on their axes in unison, or oscillated from 
side to side renege a series of complementary waves will be 
thrown by the membrane towards the tail ; the cross-section in 
the first case is an isosceles scianghe, and in the second a sector of 
a circle; the membrane of the tail is ideal similarly, so as to 
raise or ‘depress the head ; the prolate-cycloidal wave 
in fin swimming. This action of fins is best seen when pil are 
confined in a bowl, and appears to me to be only used when the 
speed required does i necessitate the use of the large muscles of 
the body ; the converse of this proposition is seen when 
makes trochoidal waves on a fluttering fi 
The geometry of body swimming may be seen in its sim implest 
in a slow-moving organism like the leech. You will observe 
ct the head is raised sar thrust forward, depressed, and drawn 
an ellipse, and then a ctmight. line. Phas a ant to 
cyli wave comes to our aid, and it hecconie pee that if 
two cylindetesl muscles be enclosed in a skin (take the swimming 
re ee 
