ing the Royal Institution, p. 32--Change in the spirit
of the enterprise after Rumford's death, p. 33--Attitude of the
earlier workers towards the question of heat as a form of motion,
p. 34--Experiments upon gases by Davy and Faraday, p. 35--Faraday's
experiments with low temperatures, p. 39--Other experiments to produce
lower temperature, p. 39--Professor De-war begins low-temperature
research, p. 39--His liquefaction of hydrogen, p. 43--Hampson's method
of producing low temperatures, p. 44--Dewar's invention of the vacuum
vessel, p. 53--Its use in retaining liquefied gases, p. 54--Changes in
physical properties of substances at excessively low temperatures, p.
56--Magnetic phenomena at low temperatures, p. 56--Changes in the color
of substances at low temperatures, p. 57--Substances made luminous by
low temperatures, p. 58--Effect of low temperatures upon the strength of
materials, p. 59--Decrease of chemical activity at low temperatures, p.
60--Olzewski's experiments with burning substances in liquid oxygen,
p. 61--Approach to the absolute zero made by liquefying hydrogen, p.
69--Probable form of all matter at the absolute zero, p. 70--Uncertain
factors that enter into this determination, p. 71.

CHAPTER IV--SOME PHYSICAL LABORATORIES AND PHYSICAL PROBLEMS

Sir Norman Lockyer and Spectroscopic Studies of the Sun and Stars, p.
73--Observations made at South Kensington by Sir Norman and his staff,
p. 74--His theories as to the influence of sun-spots and terrestrial
weather, p. 75--Spectroscopic studies of sun-spots, p. 76--Studies of
the so-called reverse lines of the spectrum, p. 78--Discovery of the new
star in the constellation of Perseus, p. 80--Spectroscopic studies
of the new star, p. 81--Professor Ramsay and the new gases, p.
82--University College in London, p. 83--Professor Ramsay's laboratory
and its equipment, p. 84--The discovery of argon, p. 86--Professor
Ramsay's work on krypton, neon, and zenon, p. 87--Discoveries of new
constituents of the atmosphere, p. 88--Interesting questions raised
by these discoveries, p. 89--Professor J. J. Thomson and the nature
of electricity, p. 92--Study of gases in relation to the conduction
of electricity, p. 93--Electricity regarded as a form of matter, p.
97--Radio-activity, p. 97--The nature of emanations from radio-active
bodies, p. 10a--The source of energy of radioactivity, p.
106--Radio-activity a