Motion the Agent in Manufactures. -- Animal Power. -- Power depending on Physical Phenomena. -- Purpose of a Machine. -- Prime Mover. -- Mechanical qualities of the Atmosphere. -- Its Weight. -- The Barometer. -- Fluid Pressure. -- Pressure of Rarefied Air. -- Elasticity of Air. -- Bellows. -- Effects of Heat. -- Thermometer. -- Method of making one. -- Freezing and Boiling Points. -- Degrees. -- Dilatation of Bodies. -- Liquefaction and Solidification. -- Vaporisation and Condensation. -- Latent heat of Steam. -- Expansion of Water in Evaporating. -- Effects of Repulsion and Cohesion. -- Effect of Pressure upon Boiling-Point. -- Formation of a Vacuum by Condensation. (1.) Of the various productions designed by nature to supply the wants of man, there are few which are suited to his necessities in the state in which the earth spontaneously offers them: if we except atmospheric air, we shall scarcely find another instance: even water, in most cases, requires to be transported from its streams or reservoirs; and food itself, in almost every form, requires culture and preparation. But if, from the mere necessities of physical existence in a primitive state, we rise to the demands of civil and social life,--to say nothing of luxuries and refinements,--we shall find that everything which contributes to our convenience, or ministers to our pleasure, requires a previous and extensive expenditure of labour. In most cases, the objects of our enjoyment derive all their excellences, not from any qualities originally inherent in the natural substances out of which they are formed, but from those qualities which have been bestowed upon them by the application of human labour and human skill. In all those changes to which the raw productions of the earth are submitted in order to adapt them to our wants, one of the principal agents is _motion_. Thus, for example, in the preparation of clothing for our bodies, the various processes necessary for the culture of the cotton require the application of moving power, first to the soil, and subsequently to the plant from which the raw material is obtained: the wool must afterwards be picked and cleansed, twisted into threads, and woven into cloth. In all these processes motion is the agent: to cleanse the wool and arrange the fibres of the cotton, the wool must be beaten, teased, carded, and submitted to other processes, by which all the foreign and coarser matter may be separated, and the fibres or threads arranged evenly, side by side. The threads must then receive a rotatory motion, by which they may be twisted into the required form; and finally peculiar motions must be given to them in order to produce among them that arrangement which characterises the cloth which it is our final purpose to produce.