Calendar: 1865-1866 Page 286

286 EVENING CLASSES and whose directions lie in the same Plane-General condi- tions of the Equilibrium of Forces whose directions lie in the same Plane-Principle of the Equality of Moments The Composition and Resolution of Parallel Forces-The Centre of Parallel Forces-The Centre of Gravity of Body Conditions determining the Stability of Body-Illustra- tions of this Situation and Motion of the Centre of Gravity of Animals as influencing their behaviour under various circumstances Balances- The Mechanical Powers statically considered-Definition of Machine-Series of Levers-Wheels and Axles-Cords and Pulleys-Inclined Plane-The Screw-The Wedge No Machine can intensify the energy of Force "What is gained in power is lost in speed Combinations of Mechanical Powers-The Force of Fric- tion Dynamics The Units of Space Time and Quantity of Matter- The term "Velocity" Newton's First Law of Motion-the Inertness of Matter-A Body cannot change the Direction or Rate of its Motion-A change of Velocity or Direction implies the existence of some exterior Force there- fore the element Time is necessarily introduced Newton's Second Law of Motion and the Parallelogram of Velocities Dynamical Force is measured by the Velocity which it will add to unit of Matter in 1" an inference from Newton's Third Law of Motion therefore the element Weight enters-Nature of the Proofs of the Laws of Motion The Force of Gravity The Motion of Projectiles-Motion down Smooth Inclined Plane-Motion in Curve-The simple Pendulum-Centrifugal Force The Elasticity of Bodies Their direct Collision Hydrostatics Propositions referring to the Nature and Effects of the Pressure exerted by Fluids The Equilibrium of Floating Bodies The Principles on which the Experimental Methods for determining the Specific Gravity of Body are based