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the mercury rise, it is a certain sign of fair weather.

11. After very great storms of wind, when the mercury has been low, it commonly rises again very fast. In settled fair weather, except the barometer sink much, expect but little rain. In a wet season, the smallest depressions must be attended to; for when the air is much inclined to showers, a little sinking in the barometer denotes more rain. And in such a season, if it rise suddenly fast and high, fair weather cannot be expected to last more than a day or two.

12. The greatest heights of the mercury are found upon easterly and north-easterly winds ; and it may often rain or snow, the wind being in these points, while the barometer is in a ris, ing state, the effects of the wind counteractingBut the mercury sinks for wind, as well as rain, in all other points of the compass.

END OF VOLUME II.

CONTENTS OF VOL. II.

Page

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HYDROSTATICS.
Conversation
I. Introduction : Definition of a Fluid ; Parti-

cles of Fluids ; Fluids incompressible;

Water forced through the Pores of Gold 9
II. Of the Weight and Pressure of Fluids :

Levels ; Fluids press equally in all direc-
tions ; Experiments

16 III. The same Subject continued

23 IV. Of the Laterai Pressure of Fluids : Lead made to swim

30 V. Of the Hydrostatical Paradox

34 VI. Of the Hydrostatical Bellows; the Weight

of pure water ; Hogshead burst by Pres.
sure ; Water Press

41 VII. Of the Pressure of Fluids against the Sides

of Vessels: in Canals; Difference between
Weight and Pressure explained and ex-
emplified

47 VIII. Of the Motion of Fluids : Water-Clocks ;

Flood-Gates ; great Pressure against the

Banks of Rivers and Canals; Puddling, &c. 53 IX. The same Subject continued : Spouting

Fluids ; Fountains ; New River ; Hamp-
stead Ponds ; London Bridge Water-

Works; Reservoir; Tottenham Court Road 58
X. Of the Specific Gravity of Bodies : Why

some Bodies swim, and others sink; Mer.
cury fourteen times heavier than Water ;
Spirits of Wine ; Water preferred as a
Standard

65

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Conversation

XI. The same Subject continued : Experiments 69
XII. The same Subject continued : Hydrostati.

cal Balance; Specific Gravity of a Guinea
and other Bodies found; why Boats swim
on water

75 XIII. The same Subject continued : Experiments 82 XIV. The same Subject continued: Archimedes's

Inventions ; Hiero's Crown; Fraud de.
tected

87 XV. The same Subject Continued : Arithmetica)

Computation; Wrong to pass bad Money 91 XVI. Of the Hydrometer: Experiments; how the

Slaves get at their Master's Rum; rectified
Spirit

97 XVII. Of the Hydrometer, and Swimming : Theo

ry of floating Vessels; Ships sink deeper
in fresh Water than in salt; Rules for
Swimming ; Water one-fourth deeper than
it appears to be

103 XVIII. Of the Siphon : Weight of Air; Tantalus's

Cup : Distiller's Crane; intermitting
Springs, &c.

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

Dr. Darwin's Description, and Prophecy;

Divers remain several hours under water 115 XX. The same Subject continued : Accidents;

Mr. Spalding and Mr. Day drowned ;
Mr. Smeaton's Invention; Mr. Walker's

Improvement; Dr. Darwin's Prophecy 119 XXI. Of Pumps: Common Pump described; deep

Wells; Dr. Darwin's Description of Pumps 123 XXII. The same Subject continued : the Forcing

Pump; Fire-Engine; Rope-Pump; Water-
Press

128'

PNEUMATICS. XXIII. Of the Nature of Air: Wind; Air in motion; how Fish swim

137

Conversation

Page
XXIV. Of the Air-Pump: Dr. Darwin's Descrip-

tion; Barometer-Gauge; Resistance of the
Air; Philosophical Hammer

141
XXV. Of the Torricellian Experiment: Experi-
ments

148
XXVI. Of the Pressure of Air : no such principle
as Suction

152
XXVII. The same Subject continued : the Trans-

ferrer; Hemispherical Cups; Fountain in
Vacuo; Bottle broken by the Pressure of
the Air; Mercury passes through the Pores
of Wood

156
XXVIII. Of the Weight of Air

161
XXIX. Of the Elasticity of Air: Experiments; Cup-
ping

166
XXX. Of the Compression of Air: Artificial Foun.

tains ; Condensing Syringe and common
Squirt compared

174
XXXI. Miscellaneous Experiments on the Air-

Pump : why Smoke and Vapours ascend;
Lungs-Glass, &c.

179
XXXII. Of the Air-Gun, and Sound : air-Guns ille-

gal; Magazine Wind-Gun; Air the medium
of Sound; Conductors of Sound; Striking
Experiment

183
XXXIII. Of Sound: Thunder; Gunpowder ; Musical

Chords; how far Sound can be heard ;
Velocity of Sound and Light ; uses to
which this knowledge may be applied

189
XXXIV. of the Speaking-Trumpet ; Speaking Fi-

196
XXXV. Of the Echo: Line of Incidence and Re
flection ; Principle of the Echo

200
XXXVI. The same Subject continued : Echoes at

Glasgow, Brussels, Thornbury Castle, Mi-
lan, &c.; Echo applied to measuring inac-
cessible distances; Whispering-Gallery at
St. Paul's; Musical Glasses

206

gures, &c.

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