Converation

Page

.....

Banks of Rivers and Canals; Pud-

dling, &c.

IX. The same Subject continued: Spouting

Fluids; Fountains; New River; Hamp-

stead Ponds; London Bridge Water-

works; Reservoir, Tottenham Court-

Road....

X. Of the Specific Gravity of Bodies: Why

some Bodies swim and others sink;

Mercury 14 times heavier than Water;

Spirits of Wine; Water preferred as a

Standard.

...

XI. The same Subject continued: Experi-

.........

ments....

XII. The same Subject continned Hydros-

tatical Balance; Specific Gravity of a

Guinea and other Bodies found; why

Boats swim on Water......

XIII. The same Subject continued: Experi-

ments....

XIV. The same Subject continued: Archi-

medes' Inventions; Hiero's Crown;

Fraud detected.......

.....

XV. The same Subject continued: Arithmeti-

cal Computations; Wrong to pass bad

Money.

XVI. Of the Hydrometer: Experiments; how

Slaves get at their Masters' Rum;

Rectified Spirit.

XVII. Of the Hydrometer, and Swimming:

Theory of floating Vessels; Ships sink

142

150

161

Conversation

deeper in fresh Water than in Salt;

Rules for swimming; Water one-fourth

deeper than it appears to be ; Pressure

of Water....

.......

XVIII. Of the Syphon: Weight of Air; Tanta-

lus's Cup; Distiller's Crane; Intermit-

ting Springs, &c......

XIX. Of the Diver's Bell: invented by Dr.

Halley; Dr. Darwin's Description, and

Prophecy; Divers; they remain several

Hours under Water.....

Page

172

186

199

XX. The same Subject continued: Accidents;

Mr. Spalding and Mr. Day drowned;

Mr. Smeaton's Invention; Mr. Walker's

Improvement; Dr. Darwin's prophecy, 207

XXI. Of Pumps: Common Pump described;

deep Wells; Dr. Darwin's Description

of Pumps.....

...... 214

XXII. The same Subject continued: The

Forcing-pump; Fire-engine; Rope-

pump; Chain-pump; Water-press.... 224

ERRATUM.

Page 67, line 16, for Conversation XX, read

Conversation XXII.

Conversation

XIII. Of the Echo: Line of Incidence and

Page

Reflection; Principle of the Echo.... 116

XIV. The same Subject continued; Echoes at

Glasgow, Brussels, Thornbury Castle,

Milan, &c.; Echo applied to measur-

ing inaccessible Distances; Whispering

Gallery at St. Paul's; Musical Glasses;

Different Tones depend upon the Num-

ber of Vibrations, and the Vibrating

Substance of the Instruments....

XV. Of the Winds; Smoke-jack, Trade

Winds, &c.; Experiments; Storms;

Velocity of Wind; Table.....

128

148

XVI. Of the Steam-engine: when and by whom

invented; Mr. Watt's improvement.. 156

......

XVII. The same Subject continued...

XVIII. The same Subject, and Papin's Digester :

Whitbread's Brewery; Accidents by

Steam

169

178

200

XIX. Of the Barometer: Fluctuation of the

Mercury; the Vernier ; Rules for pre-

dicting the Changes of the Weather.. 189

XX. Application of the Barometer to the

measuring of Altitudes

XXI. Of the Thermometer; Fahrenheit's Scale 211

XXII. The same Subject; Wedgewood's Scale

of Heat; Fahrenheit and Reaumur's

Thermometer's compared.......

XXIII. Of the Pyrometer and Hygrometer.... 230

XXIV. Of the Rain-guage, and Rules for judging

of the Weather

APPENDIX.

Of Air, as a Vehicle of Heat and Moisture. Of

Rain-Dew-Meteoric Stones ...

220

242

253

CONVERSATION I.

OF THE NATURE OF AIR.

FATHER-CHARLES-EMMA.

FATHER.

That branch of natural philosophy which is called Pneumatics, treats of the nature, weight, pressure, and spring of the air which we breathe, and of the several effects dependent upon these properties.

Charles. You told us, a few days ago, that the air, though to us invisible, is a fluid; but it surely differs very much from those fluids which you conversed upon when treating of hydrostatics.

is formed of two Greek words which signify water, and the science which considers the weight of bodies. But hydrostatics, as a branch of natural philosophy, treats of the nature, gravity, pressure, and motion of fluids in general; and of the methods of weighing solids in them.

Charles. Is this an important part of knowledge?

Father. Taken in this extensive sense it yields to none as to its real importance. And the experiments which I shall show you are curious and highly amusing.

Emma. Shall we be able to repeat them ourselves?

Father. Most of them you will, provided you are very careful in using the instruments, almost all of which are made of glass. I ought to tell you that many writers divide