THE MINOR PLANETS page 141 



Classification of the Planets. — Mercury. — Transit over the Sun. — Relative Position with regard to 

 the Sun. — Difficulty of observing it. — Vehus. — Diurnal Motion of Venus and Mercury indicated 

 by the Shadows of Mountains. — Direction of the Axis of Rotation. — Seasons, Climates, and 

 Zones. — Orbits and Transits of Mercury and Venus. — Mountains on Mercury and Venus. — Influ- 

 ence of the Sun at Mercury and Venus. — Twilight on Mercury and Venus. — Mars. — Atmosphere 

 of Mars. — Physical Constitution of Mars. — Has Mars a Satellite? — Appearance of the Sun at 

 Mars. — Its close Analogy to the Earth. 



WEATHER ALMANACS 157 



Merits of Weather Almanacs. — Excitability of the London Public. — Fright produced by Biela's 

 Comet. — London Water Panic. — London Air Panic. — London Bread Panic. — Rage for Weather 

 Almanacs. — Patrick Murphy's Pretensions. — Examination of the Predictions of the Weather 

 Almanac. — Their Absurdity. — Comparison of the Predictions with the Event. — Morrison's 

 Weather Almanac. — Charlatanism of these Publications. — Great Frost of 1838 in London. — 

 Other Visitations of Cold. 



HALLEY'S COMET 169 



Predictions of Science. — Structure of the Solar System. — Motion of Comets. — How to identify 

 them. — Intervals of their Appearance. — Halley's Comet. — Its History. — Newton's Conjectures. — 

 Sagacity of Voltaire. — Halley's Researches. — Foretells the Reappearance of the Comet in 1759. — 

 Principle of Gravitation applied to its Motion by Clairaut. — Researches of that Mathematician. — 

 Anecdotes of Lalande and Madame Lepaute. — Minute and circumstantial Prediction of the Re- 

 appearance of Halley's Comet. — Discovery of the Planet Herschel anticipated by Clairaut. — 

 Reappearance of the Comet at the predicted Time. — Second Prediction of its Return in 1835. — 

 Prediction fulfilled. — Observations on its Appearance in 1835. 



THE ATMOSPHERE 191 



Atmospheric Air is material. — Its Color. — Cause of the blue Sky. — Cause of the green Sea. — Air 

 has Weight. — Experimental Proofs. — Air has Inertia. — Examples of its Resistance. — It acquires 

 moving Force. — Examples of its Impact. — Air is impenetrable. — Experimental Proofs. — Elastic 

 and compressing Forces equal. — Limited Height of the Atmosphere. — Elasticity proportioned to 

 the Density. — Experimental Proofs. — Internal and external Pressure on close Vessels contain- 

 ing Air. 



THE NEW PLANETS 203 



Indications of a Gap in the Solar System. — Bode's Analogy. — Prediction founded upon it. — Piazzi 

 discovers Ceres. — Dr. Olbers discovers Pallas. — Harding discovers Juno. — Dr. Olbers discovers 

 Vesta. — Indications afforded by these Bodies of the Truth of Bode's Predictions. — Fragments 

 of a broken Planet. — Others probably still undiscovered. — Their ultra-zodiacal Motions. — Their 

 Eccentricities. — They are probably not globular. — Other Singularities of their Appearance. 



THE TIDES 209 



Correspondence between the Tides and Phases of the Moon shown by Kepler. — Erroneous popular 

 Notion of the Moon's Influence. — Actual Manner in which the Moon operates. — Influence of the 

 Sun. — Combined Action of the Sun and Moon. — Spring Tides. — Counter-action of the Sun and 

 Moon. — Neap Tides. — Priming and Lagging of the Tides. — Discussions at the British Association. 

 — Whewell's Researches. — Effect of Continents and Islands on the Tides. — General Progress 

 of the Great Tidal Wave.— Velocity of the Tidal Wave.— Range of the Tide. 



LIGHT 221 



Structure of the Eye. — Manner in which distant Objects become visible. — Corpuscular Theory. — 

 Undulatory Theory. — Its general Reception. — Velocity of Light. — Account of its Discovery by 

 Roemer. — Measurement of the Waves of Light by Newton. — Color produced by Waves of 

 different Magnitudes. — Magnitudes of Waves of different Color. — Summary View of the Corpus- 

 cular Theory. — Summary View of the undulatory Theory. — These Theories compared. — Discov- 

 eries of Dr. Young. — Discoveries of Malus, Arago, Poisson, Herschel, and Airy. — Relations of 

 Light and Heat. 



THE MAJOR PLANETS .T^.. % 235 



Space between Mars and Jupiter. — Jupiter's Distance and Period. — His Magnitude and Weight. 

 —His Velocity.— Appearance of his Disk.— Day and Night on Jupiter.— Position of his Axis.— 

 Absence of Seasons. — His telescopic Appearance. — His Belts. — Causes of his Belts. — Currents 

 in his Atmosphere. — Madler's telescopic Views of Jupiter. — Appearance of the Sun as seen from 

 Jupiter. — His Satellites. — The Variety of his Months. — Magnificent Appearance of the Moons as 

 seen from Jupiter. — Their Eclipses. — Saturn. — His diurnal Rotation. — Appearance of the Sun 

 as seen from him. — His Atmosphere. — His Rings. — Their Dimensions. — Biot's Explanation of 

 their Stability. — Herschel's Theory of the same. — Appearances and Disappearances of the 

 Rings. — Various Phases of the Rings. — Saturn's Satellites. — Herschel or Uranus. — His Dis- 

 tance and Magnitude. — His Moons. — Reasons why there is no Planet beyond his Orbit. 



REFLECTION OF LIGHT 257 



Ray of Light. — Pencil of Light. — Reflection. — Irregular Reflection. — Regular Reflection. — Different 

 Powers of Reflection in different Bodies. — Reflection at plane Surfaces. — Its Laws. — Image of 

 an Object in a plane Reflector. — Reflection of curved Surfaces. — Concave Reflectors. — Convex 

 Reflectors. — Images in spherical Reflectors. — Illusion of the Air-drawn Dagger. — Effects of com- 



