CONTENTS OF VOLUME II. 13 



Modes of Graduation. Alcohol Thermometers. Difficulty of fixing the boilintr Point. Useful- 

 ness of the Thermometer. History of its Invention. Methods of comparing Scales of different 

 Thermometers. 



ATMOSPHERIC ELECTRICITY PAGE 147 



On the Electricity of the Atmosphere in clear Weather. Connexion between Electricity and Me- 

 teorology. Apparatus for observing the Electricity of the Atmosphere. Insulated elevated Rod. 

 Portable Apparatus made of a fishing Rod. Saussure's Electroscope and his Mode of estimating 

 the Value of the Divergences. Occasional Use of the Galvanometer. The ordinary StnJe of the 

 Atmosphere. Volta's Theory of the Origin of Atmospheric Electricity. Inadequacy ot the tTieo 

 ry of Chemical Origin. The Author's Supgestion of the probable Influence of Friction. Diurnal 

 Variation of the Electricity. Periodical hourly Variation Representation of the Rate of Varia- 

 tion. Maxima and Minima at a given Parallel. Schubler's Observations. Annual Variation of 

 the Electricity. Variation of the daily Maxima and Minima. Arago's Repetition of Schubler's 

 Observations. Local Variations of the Electricity Influence of particular Localities, Buildings, 

 &c. No satisfactory Explanation yet given of the Variations. Correspondence between Electric 

 and Magnetic Variations. Becquerel's Explanation of the Phenomena of Variation. Distribu- 

 tion of Electricity of the Air. Negative State of the Earth. Character of the lower Stratum of 

 Air. Increase of Electric Charge in the higher Strata of Air. Decrease in the lower Strata. 

 Comparative Electric Character of different Strata. Formulae for the comparative Electricity of 

 two Strata. Electricity of the Air in clouded Weather. Preliminary. Schubler's Observations. 

 Table of Observations explained. 



EVAPORATION . . . . " 161 



Erroneously ascribed to Chemical Combination. Takes place from the Surface. Law discovered 

 by Dalton extended to all Liquids. Limit of Evaporation conjectured by Faraday. Hygrome- 

 ters. Various Phenomena explained by Evaporation. Leslie's Method of freezing. Examples 

 in the useful Arts. Methods of Cooling by Evaporation. Dangerous Effects of Dampness. 

 Wollaston's Cryophorus Pneumatic Ink-Bottle. Clouds. Dew. 



CONDUCTION OF HEAT ." 177 



Conducting Powers of Bodies. Liquids Non- Conductors. Effect of Feathers and Wool on Ani- 

 mals. Clothing. Familiar Examples. 



RELATION OF HEAT AND LIGHT 185 



Probable Identity of Heat and Light. Incandescence. Probable Temperature of Gases cannot 

 be made Incandescent The Absorption and Reflection of Heat depend on Color. Burning 

 Glass Heat of Sun's Rays. Heat of artificial Light. Moonlight. Phosphorescence. 



ACTION AND REACTION 195 



Inertia in a single Body. Consequences of Inertia in two or more Bodies. Examples. Effects of 

 Impact. Motion not estimated by Speed or Velocity alone. Examples. Rule for estimating the 

 Quantity of Motion. Action and Reaction. Examples of. Velocity of two Bodies after Impact. 

 Magnet and Iron. Feather and Cannon-Bali impinging. Newton's Laws of Motion. Inu- 

 tility of. 



COMPOSITION AND RESOLUTION OF FORCE 205 



Motion and Pressure. Force Attraction. Parallelogram of Forces. Resultant. Components 

 Composition of Force. Resolution of Force Illustrative Experiments. Composition of Pres- 

 sures. Theorems regulating Pressures also regulate Motion. Examples Resolution of Motion. 

 Forces in Equilibrium. Composition of Motion and Pressure Illustrations. Boat in a Cur- 

 rent Motions of Fishes. Flight of Birds. Sails of a Vessel. Tacking. Equestrian Feats. 

 Absolute and relative Motion. 



CENTRE OF GRAVITY 219 



Terrestrial Attraction the combined Action of parallel Forces. Single equivalent Force. Exam- 

 ples. Method of finding the Centre of Gravity. Line of Direction. Globe. Oblate Spheroid 

 Prolate Spheroid. Cube. Straight Wand. Flat Plate. Triangular Plate. Centre of Gravity 

 not always within the Body. A Ring. Experiments Stable, instable, and neutral Equilibrium. 

 Motion and Position of the Arms and Feet. Effect of the Knee-joint. Positions of a Dancer. 

 Porter under a Load. Motion of a Quadruped. Rope Dancing. Centre of Gravity of two Bi d- 

 ies separated from each other. Mathematical and experimental Examples. The Conservntic: 

 of the Motion of the Centre of Gravity. Solar System. Centre of Gravity sometimes called Cen- 

 tre of Inertia. 



THE LEVER AND WHEEL-WORK 241 



Simple Machine. Statics. Dynamics. Force. Power. Weight. The Lever. Cord. Inclined 

 Plane. Arms. Fulcrum. Three kinds of Lever. Crow Bar Handspike. Oar. Nut-Crack- 

 ers. Turning Lathe. Steelyard. Rectangular Lever. Hammer. Load between two Bearers. 

 Combination of Levers. Equivalent Lever. Wheel and Axle. Thickness of the Rope. Ways 

 of applying the Power. Projecting Pins. Windlass. Winch. Axle. Horizontal Wheel. 

 Tread-Mill. Cranes. W ater- Wheels. Paddle- Wheel Rachet- Wheel. Rack Spring of a 

 Watch Fusee. Straps or Cords. Examples of. Turning Lathe. Revolving Shafts. Spinning 

 Machinery. Saw-Mill. Pinion. Leaves. Crane. Spur- Wheels Crown-Wheels. Bevelled 

 W heels. Huntir .,- 3og. Chronometers. Hair-Spring. Balance- Wheel. 



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