32 
C. L. Herrick 
The appearance may endure for hours and may be traced for scores 
of miles over the trackless plain. The sand in it (that is the mate- 
rial) is continually changing as is the component air. The little 
vortex is the result of the union of equilibrated forces, and is just 
as much a real object as is a tree or a man. It is an individual, 
but its unity obviously consists in the perpetuation of a definite 
form of coordinated activity. The currents of air which compose 
it are eventually merged in the general system of atmospheric 
currents, and the individuality is lost. It is possible to imagine 
a set of intricately coordinated currents of force so adjusted as 
to give rise to a property which we call feeling or consciousness. 
The human organism is especially adapted to produce the back- 
ground of constant experience across which is flung the flickering 
image of the passing events. 
In a uniform medium, as has abundantly been shown, the only 
condition of individuality is that of vector activity. Vortex 
rings serve as illustrations. The discussion of vortex atoms has 
brought out this peculiarity. Two forms of activity appeal to our 
senses; first, progressive or translational or molar; second, self- 
centered or vector activities. In the first case the point is con- 
ceived as moving in a right line or some other progressive manner 
so that the motion is indeterminate ; in the second case the motion 
is cyclical and the center of reference is stable. In ordinary 
parlance, when a body falls, the motion is of the first sort, but 
when brought to rest the motion is transformed into the second 
state. The body is in a state of rest and with reference to adjacent 
bodies is in equilibrium. 
Vector motions have a remarkable stabilizing power, as witness, 
for example, the gyroscope. The two classes of motion have been 
called molar and molecular respectively, but this perhaps involves 
too large a hypothetical step. The crude illustrations used, may 
serve to show at least that the same force may have a conservative 
power in one phase and a dispersive power in another. But let 
one take the still simpler illustration of a solenoid. A current 
of electricity passing through a straight wire produces, it is true, 
an induction-effect on the neighboring metals ; but, when the same 
current is forced to pass through a spiral path, the complex acquires 
2° Some of the pages which follow have appeared under the title ‘^The Nature of 
the Soul and the Possibility of a Psycho-mechanic/' in the Psychological Review, 
vol. 14, no. 3, May, 1907. 
