MEASUREMENTS

Sec. 1.  Metrology:  Lord Kelvin’s view of its necessity—­ Its definition

Sec. 2.  The Measure of Length:  Necessity for unit—­
Absolute length—­History of Standard—­Description of
Standard Metre—­Unit of wave-lengths preferable—­The
International Metre

Sec. 3.  The Measure of Mass:  Distinction between mass and weight—­Objections to legal kilogramme and its precision—­Possible improvement

Sec. 4.  The Measure of Time:  Unit of time the second—­Alternative units proposed—­Improvements in chronometry and invar

Sec. 5.  The Measure of Temperature:  Fundamental and derived units—­Ordinary unit of temperature purely arbitrary—­Absolute unit mass of H at pressure of 1 m. of Hg at 0 deg.  C.—­Divergence of thermometric and thermodynamic scales—­Helium thermometer for low, thermo-electric couple for high, temperatures—­Lummer and Pringsheim’s improvements in thermometry.

Sec. 6.  Derived Units and Measure of Energy:  Importance of erg as unit—­Calorimeter usual means of determination—­Photometric units.

Sec. 7.  Measure of Physical Constants:  Constant of gravitation—­Discoveries of Cavendish, Vernon Boys, Eoetvoes, Richarz and Krigar-Menzel—­Michelson’s improvements on Fizeau and Foucault’s experiments—­ Measure of speed of light.

CHAPTER III

PRINCIPLES

Sec. 1.  The Principles of Physics:  The Principles of Mechanics affected by recent discoveries—­Is mass indestructible?—­Landolt and Heydweiller’s experiments —­Lavoisier’s law only approximately true—­Curie’s principle of symmetry.

Sec. 2.  The Principle of the Conservation of Energy:  Its evolution:  Bernoulli, Lavoisier and Laplace, Young, Rumford, Davy, Sadi Carnot, and Robert Mayer—­Mayer’s drawbacks—­Error of those who would make mechanics part of energetics—­Verdet’s predictions—­Rankine inventor of energetics—­Usefulness of Work as standard form of energy—­Physicists who think matter form of energy—­ Objections to this—­Philosophical value of conservation doctrine.

Sec. 3.  The Principle of Carnot and Clausius:  Originality of Carnot’s principle that fall of temperature necessary for production of work by heat—­ Clausius’ postulate that heat cannot pass from cold to hot body without accessory phenomena—­Entropy result of this—­Definition of entropy—­Entropy tends to increase incessantly—­A magnitude which measures evolution of system—­Clausius’ and Kelvin’s deduction that heat end of all energy in Universe—­Objection to this—­ Carnot’s principle not necessarily referable to mechanics —­Brownian movements—­Lippmann’s objection to kinetic hypothesis.

Sec. 4.  Thermodynamics:  Historical work of Massieu, Willard Gibbs, Helmholtz, and Duhem—­Willard Gibbs founder of thermodynamic statics, Van t’Hoff its reviver—­The Phase Law—­Raveau explains it without thermodynamics.