54: On the Principles of the Science of Motion. 
of nature are mutually dependent, have one common origin, or 
rather are different manifestations of one fundamental power* ” 
—become, at least for all the phenomena of Motion as distin- 
guished from those of Growth, a scientific truth ? 
81. For the sake of distinctly defining by its relations the 
Science of Motion, a few words may be added on the Classifica- 
tion of the Scicnces proposed by the author. The general di- 
visions of each of the two great classes—the Natural and Humane 
Sciences—are (A) the Systematic, (B) the Descriptive, and (C) 
the Historic Sciences. 
The Systematic Natural Sciences are the sciences of (I.) Mo- 
tion, (II.) Growth, (III.) Species (“the Classificatory Sciences” 
of Whewell) t+. 
The twofold subdivision of each of the three sciences of 
motion will be evident from the foregoing. 
Hach of these rational sciences, as well as those making up 
the Science of Growth, have a corresponding applied science. 
The Science of Motion, as a distinct science, and not as merely. 
a general name for the sciences of mechanics, physics, and che- 
mics, has a twofold division. 
Under the first, the general relations, laws, or principles of 
motion, without regard to the particular conditions of its cause, 
would be considered: such general principles, for mstance, as 
Galileo’s laws of Inertia, and of the Composition of Motions ; 
Newton’s law of the Equality of Action and Reaction ; its genera- 
lization in D’Alembert’s principle; Jean Bernoulli’s (?)¢ prin- 
ciple of Virtual Velocities; Varignon’s geometrical theorem on 
Moments; Poinsot’s theory of Couples ; Newton’s principle of the 
Conservation of the movement of the Centre of Gravity ; Kepler’s 
principle of Areas ; Laplace’s theorem on the Invariable Plane; 
Euler’s on Moments of Inertia, and Principal Axes ; Huygens’s 
principle of the Conservation of Vires vive; Daniel Bernoulli’s 
theorem on the Coexistence of small Oscillations, &c. 
The object of the second division cf the General Science of 
Motion would be the generalization of the conditions giving rise 
to the various Forces of Motion, mechanical, physical, and che- 
mical, and their correlations. This paper, therefore, has treated 
of the principles of but one division of the science. 
_ The divisions of the special science of Mechanics, that on 
Solids, and that on Fluids, would be conveniently considered in 
kinematical §, statical, and dynamical sections. 
* Faraday, ‘ Experimental Researches,’ 2702. 
t+ History of the Inductive Sciences, iii. p. 211. 
t Poisson, Traité de Mécanique, i. p. 654. 
§ See Ampére’s Essaz sur la Philosophie des Sciences ; Willis’s preface 
to his ‘ Principles of Mechanism,’ and the arrangement of Rankine’s 
‘Manual of Applied Mechanics’ (Encyc. Metrop.). 
