36 KANSAS ACADEMY OF SCIENCE. 
comes from the sky overhead than from that low down would also tend to an 
impression of greater nearness for the former. 
Scientific explanation is nothing more than the bringing together the more 
closely related facts. When we seek such an explanation we, endeavor to dis- 
cover relationships between the facts. Consider another illustration: 
It is frequently asked why our visual impressions of objects about us are not 
inverted, inasmuch as the image on the retina of the eye can clearly be demon- 
strated to be inverted. Inverted with respect to what? is our first question. 
The reply may be: Inverted with respect to the object itself. The antonym to 
the term ‘‘inverted”’ is ‘‘erect,’? which means the normal position of the object 
with reference to the horizon and to other associated objects. In the picture 
formed on the retina of the eye these external relationships as they appear are 
not disturbed, and therefore how could the object contemplated be considered as 
inverted? To the acrobat standing on his head the world does not appear upside 
down, for he recognizes that it is he who is inverted for the time being, while all 
other objects hold a normal position with reference to each other. 
It was only by carefully tracing the relativity of phenomena that Count Rum- 
ford and William Robert Grove and Julius Robert Mayer were enabled to arrive 
at that grandest of scientific generalizations, that all energy is correlated and is 
forever conserved. They recognized that all energy is one and the same, how- 
ever variously manifested. Energy is the capacity which moving bodies have, 
by virtue of their mass and motion, of imparting movement to other bodies. 
Hence they recognized but one kind of energy, that which afterward received 
the name of ‘‘kinetic’’ energy. 
All energy is kinetic, for displacement of a body through space can be accom- 
plished only by one moving body imparting its motion to another, whether that 
motion be of a mass, and so known as mechanical; or of molecules, and so known 
as heat; or of atoms, and therefore known as chemism; or of ether vibrations, 
and known as light, electricity, magnetism, or gravity. The physical concept 
‘‘energy’’? must ever hold motion as an essential property — motion of mass, of 
molecules, atoms, or ether particles. I am aware that an expression known as 
‘‘ potential energy” has crept into physical discussions and has been copied from 
one text-book to another now for a generation or two, and seems likely to be con- 
tinued by compilers of texts on natural philosophy for some generations to come. 
As I endeavored to point out before this Academy six years ago, at the Ottawa 
meeting, I still maintain that there is no such thing as potential energy, except 
as we may ina loose way regard all energy as potential in the sense that it is 
possible, as heat, light, electricity, or gravity, to be intertransformed. As ordi- 
narily presented in texts on physics, the concept ‘‘ potential energy”’ is a false 
correlation, and the result of surprisingly slovenly thought. 
To illustrate: A lad holds a ball in hand which he purposes to toss in air. 
Were I to assert that that ball possessed energy of any kind in relation to the 
conditions presented —those of the boy’s hand and the plane of its position as 
the plane of reference, you would rightly pronounce the statement absurd. 
Please, then, where is the difference of related conditions after the ball has been 
tossed upward and rests for an instant poised in mid-air in the hand of gravity? 
And yet, under the latter conditions, we are told that the ball possesses a pe- 
culiar energy —‘‘ potential energy ’’—the result of the conversion of the kinetic 
energy it possessed at the beginning of itsascent. Now what is the true relation 
of the facts, which relation has been overlooked in presenting the false deduc- 
tions called ‘potential energy’’? They are as follows: The ball in rising is 
doing work against the force of gravity; that is, it is accomplishing ether dis- 
