-Velocity of Falling Bodies.-Momentum.-Action and Reac-

tion Equal-Elasticity of Bodies.-Porosity of Bodies.-Re-

flected Motion.-Angles of Incidence and Reflection.

Page 49

CONVERSATION IV.

On Compound Motion.

Compound Motion the result of two opposite forces.-Of Circu-

lar Motion, the result of two forces, one of which confines the

body to a fixed point.-Centre of motion, the point at rest

while the other parts of the body move round it.-Centre of

Magnitude, the middle of a body.-Centripetal Force, that

which confines a body to a fixed central point.-Centrifugal

Force, that which impels a body to fly from the centre.-Fall

of Bodies in a Parabola.-Centre of Gravity, the Centre of

Weight, or point about which the parts balance each other.

Page 69

CONVERSATION V.

On the Mechanical Powers.

Of the Power of Machines.-Of the Lever in general.-Of the

Lever of the first kind, having the Fulcrum between the Power

and the weight.-Of the Lever of second kind, having the

Weight between the power and the Fulcrum.-Of the Lever

of the third kind, having the power between the Fulcrum and

the Weight. Of the Pulley-Of the Wheel and Axle-Of

the inclined Plane.-Of the Wedge.—Of the Screw.

Page 81

CONVERSATION VI.

ASTRONOMY.

Causes of the Earth's Annual Motion.

Of the Planets, and their motion. Of the Diurnal motion of the

Earth and Planets.

Page 107

CONVERSATION VII.

On the Planets.

Of the Satellites or Moons.-Gravity diminishes as the Square of

the Distance.-Of the Solar System.-Of Comets.-Constella-

tions, signs of the Zodiac.—Of Copernicus, Newton, &c.

Page 121

CONVERSATION VIII.

On the Earth.

Of the Terrestrial Globe. Of the Figure of the Earth.-Of the

Pendulum.-Of the Variation of the Seasons, and of the

Length of Days and Nights.-Of the Causes of the Heat of

Summer.-Of Solar, Siderial, and Equal or Mean Time.

Page 137

CONVERSATION IX.

On the Moon.

Of the Moon's Motion.-Phases of the Moon.-Eclipses of the

Moon.-Eclipses of Jupiter's Moons.--Of the Latitude and

Longitude. Of the transits of the inferior Planets. Of the

Tides.

Page 163

CONVERSATION X.

HYDROSTATICS.

On the Mechanical Properties of Fluids.

Definition of a Fluid.-Distinction between Fluids and Liquids.-

Of Non-Elastic Fluids, scarcely susceptible of Compression.—

Of the Cohesion of Fluids.-Of their Gravitation.-Of their

Equilibrium.-Of their Pressure.-Of Specific Gravity.-Of

the Specific Gravity of Bodies heavier than Water. Of those

of the same weight as Water.-Of those lighter than Water.-

Of the Specific Gravity of Fluids.

Page 177

CONVERSATION XI.

Of Springs, Fountains, &c.

Of the Ascent of Vapor and the Formation of Clouds.-Of the

Formation and Fall of Rain, &c.—Of the Formation of Springs.

-Of Rivers and Lakes.-Of Fountains.

Page 198

CONVERSATION XII.

PNEUMATICS.

On the Mechanical Properties of Air.

-

Of the Spring or Elasticity of the Air.-Of the Weight of the

Air-Experiments with the Air Pump.-Of the Barometer

Mode of Weighing Air-Specific Gravity of Air-Of Pumps.

-Description of the Sucking Pump.-Description of the

Forcing Pump.

Page 205

Of Wind in General.-Of the Trade Wind.-Of the Periodical

Trade Winds Of the Aerial Tides.-Of Sound in General.-

Of Sonorous Bodies-Of Musical Sounds.-Of Concord or

Harmony, and Melody.

Page 219

CONVERSATION. XIV.

On Optics.

Of Luminous, Transparent, and Opaque Bodies.-Of the Radia-

tion of Light.-Of Shadows.-Of the Reflection of Light.—

Opaque Bodies seen only by Reflected Light.-Vision Explain-

ed.--Camera Obscura.-Image of Objects on the Retina.

Page 237

CONVERSATION XV.

On the Angle of Vision, and Reflection of Mirrors.

Angle of Vision.-Reflection of Flain Mirrors.-Reflection of

Convex Mirrors.-Reflection of Concave Mirrors.

Page 253

CONVERSATION XVI.

On Refraction and Colors.

Transmission of Light by Transparent Bodies.-Refraction.-m

Refraction of the Atmosphere -Refraction of a Lens-Re-

fraction of the Prism.-Of the Colors of Rays of Light.-Of the

Colors of Bodies.

Page 271

CONVERSATION XVII.

OPTICS.

On the Structure of the Eye, and Optical Instruments.
Description of the Eye-Of the Image on the Retina.-Refraction

of the Humors of the Eye.-Of the Use of Spectacles. Of the
Single Microscope. Of the Double Microscope. Of the Solar
Microscope.--Magic Lanthorn.-Refracting Telescope.-Re-
flecting Telescope,