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CONTENTS.

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MIXTURE OF GASES.— VAPOUR. .

Boyle's law holds for a mixture of gases, 74; gas absorbed by a liquid

in contact with it, 75; relation between change of temperature and change

of volume in all substances, 76; meaning of the term thermometer,

77; mercurial thermometer, 78; filling the thermometer; comparative

expansions of substances, 79; temperature measured by the thermometer,

80; expansion of water, 81; proof of the formula p= kp(1 + at), 82;

relations between the heat absorbed, the resulting temperature and the

mass, for a uniform substance, 83; algebraical expression of the same,

ditto for a compound substance, 85; specific heat, 86; algebraical

formula, 87; specific heat of gases, 88; all substances made to ex-

perience the solid liquid or gaseous state by the application of correspond-

ing amount of heat, 89; vapour, 90; saturation density, and its dew-

point, 91; under what circumstances vapours follow Boyle's law, or not,

92 ; gases, 93; the preceding results independent of the number of gases

present, 94, 95; ebullition of water, 96; algebraical formula connecting

the pressures and temperatuure for a mixture of gas and vapour, 97 ; latent

heat, 98; effects produced by absorption of heat in evaporation, 99; con-

traction produces the opposite results to dilatation, 100; hygrometrical

state of the atmosphere; 101; Clouds, 102; Rain, 103; causes producing

these effects, 104; Snow and Hail, 105; Dew, Hoar-frost, &c., 107; Con-

duction, Convection, and Radiation of heat, 108; cause of dew, &c., 109;

Dew-point, 110; results of the law of expansion in water, 111.

General Examples

Answers to the Examples

HYDROSTATICS.

SECTION I.

PRELIMINARY DEFINITIONS AND EXPLANATIONS.

1. DEF. A fluid is a collection of material particles so situated in contact with each other as to form a continuous mass, and such that the application of the slightest possible force to any one of them is sufficient to displace it from its position relative to the rest.

That part of Statics, where a fluid appears as the principal means of transmission of force, is termed Hydrostatics. The law of that transmission must, like the law of transmission by a rigid body, by a free rod or string, or by contact of surfaces, &c., be established by experiment.

The mutual forces called into action by the contact of surfaces are in Statics called pressures : this term is used in the same sense in Hydrostatics, where it is applied to denote the forces of resistance, which adjacent particles of the fluid exert, either upon one another, or upon rigid surfaces in contact with them. The nature of the reaction between a rigid surface and a fluid in contact with it might perhaps be arrived at by the aid of analysis from the above definition. But such an investigation, even if entirely satisfactory in itself, would

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