152 KANSAS CITY REVIEW OF SCIENCE. 
the head is bent far forward ; then by reaction like a pendulum it rises, swings 
back and passes beyond its original position to a point about as low as when bent 
farthest forward. The movement may be repeated many times, but we have 
seen all that that particular head does. When erect it is at its highest point and 
when bent farthest forward it is at its lowest point. We learn from this that the 
heads of grain are performing movements which are transverse to the line along 
which the wave is moving. In like manner do the particles of a rope move 
when you catch hold of one end of the rope and cause a wave motion along its 
entire length. And water waves are caused in the same way. 
Again, take an elastic wire, coil it into a spiral, support one end firmly, to 
the other end fasten a weight, and cause the weight to vibrate up and down by 
pulling it downward and then freeing it. Evidently the coils of the spiral are at 
one time stretched apart and at another time crowded together, as the weight 
vibrates up and down. ‘That is, the particles instead of moving /¢ransverse to the 
line of wave motion are moving paralle/ with it. | 
To sum up, then, there are two classes of undulatory movements: 
1—Those in which the elements of the wave move transverse to the line of 
direction of the wave; and 
2—Those in which the elements of the wave move parallel with the line of 
direction of the wave, i. e. there is alternate cond: nsation and rarefaction among 
the elements of the wave. 
. Now there are four classes of material substance with which we have to deal: 
t— Masses. 
2— Molecules. 
3—Atoms. 
4—Radiant matter, called ‘‘ Ether.” 
We look up to those great masses we call stars and: learn that they are for- 
ever in motion. We explain the solid, the liquid and the gaseous conditions of 
matter by saying that the molecules are in motion and are only closer together in 
the solid than in the fluid. By analogy and by the researches of such men as 
Crookes and others, we reason that atoms and ether particles.are likewise in con- 
tinual motion. ‘Thus we are led to conclude that in matter nowhere ‘“‘ can rest 
be found.” 
The constituent particles of all matter are forever unstilled. 
If Ihave made myself understood thus far, I shall now proceed to use 
these facts in explanation of the actions of our various organs of sense. I shall 
try to demonstrate that these various organs of sense are so endowed that each 
takes cognizance of certain rates of undulatory motion and transmits its impres- 
sions to the brain. How these impressions are transmitted to the brain, I shall 
not pretend to say--that is beyond the scope of material science; but I do want 
to show that the nerves of these organs are. affected by and receptive of undula- 
tory movements within limits ordained for each particular organ. In the cases 
of the ear and the eye, this is already an accepted theory. Let us state the 
reasoning in the cases of these briefly. 
