inning of modern electricity--The construction of
the voltaic pile--Nicholson's and Carlisle's discovery that the galvanic
current decomposes water--Decomposition of various substances by Sir
Humphry Davy--His construction of an arc-light--The deflection of the
magnetic needle by electricity demonstrated by Oersted--Effect of
this important discovery--Ampere creates the science of
electro-dynamics--Joseph Henry's studies of electromagnets--Michael
Faraday begins his studies of electromagnetic induction--His famous
paper before the Royal Society, in 1831, in which he demonstrates
electro-magnetic induction--His explanation of Arago's
rotating disk--The search for a satisfactory method of storing
electricity--Roentgen rays, or X-rays.

CHAPTER VIII. THE CONSERVATION OF ENERGY

Faraday narrowly misses the discovery of the doctrine of
conservation--Carnot's belief that a definite quantity of work can be
transformed into a definite quantity of heat--The work of James Prescott
Joule--Investigations begun by Dr. Mayer--Mayer's paper of 1842--His
statement of the law of the conservation of energy--Mayer and
Helmholtz--Joule's paper of 1843--Joule or Mayer--Lord Kelvin and the
dissipation of energy-The final unification.

CHAPTER IX. THE ETHER AND PONDERABLE MATTER

James Clerk-Maxwell's conception of ether--Thomas Young and
"Luminiferous ether,"--Young's and Fresnel's conception of transverse
luminiferous undulations--Faraday's experiments pointing to the
existence of ether--Professor Lodge's suggestion of two ethers--Lord
Kelvin's calculation of the probable density of ether--The vortex theory
of atoms--Helmholtz's calculations in vortex motions--Professor
Tait's apparatus for creating vortex rings in the air---The ultimate
constitution of matter as conceived by Boscovich--Davy's speculations
as to the changes that occur in the substance of matter at different
temperatures--Clausius's and Maxwell's investigations of the
kinetic theory of gases--Lord Kelvin's estimate of the size of the
molecule--Studies of the potential energy of molecules--Action of gases
at low temperatures.

APPENDIX

A HISTORY OF SCIENCE

BOOK III. MODERN DEVELOPMENT OF THE PHYSICAL SCIENCES

With the present book we enter the field of the distinctively modern.
There is no precise date at which we take up each of the successive
stories, but the main sweep of developme