Household administration : its place in the higher education of women / edited by Alice Ravenhill and Catherine J. Schiff.

Date:
[1910]
Catalogue details

Licence: In copyright

Credit: Household administration : its place in the higher education of women / edited by Alice Ravenhill and Catherine J. Schiff. Source: Wellcome Collection.

    87/332
    beaker the water will go to the bottom of the beaker and will displace the oil and lift it up so that the oil will float on the water ; the oil may be lifted to any height we please if sufficient water be poured in to lift it to that height. If a single drop of oil be introduced into the water by means of a pipette and be liberated at the bottom of the beaker the water will close in under it, and lift it up to the surface. In both cases the oil “ rises ” through the water. Oil, however, has no tendency to u rise ” by itself, and in this case it lay motion- less until it was lifted by the heavier fluid. We may use colloquial language when describing phenomena if we bear in mind what is really taking place. A balloon “ rising through the air is exactly analogous to the drop of oil in the water. The balloon is, bulk for bulk, lighter than air ; the air therefore closes in under it and lifts it just as the water lifted the bubble of oil. EFFECTS OF CHANGES OF TEMPERATURE ON AIR Let us apply this to air. Air when warmed expands, and therefore warm air is, bulk for bulk, lighter than cold air. Warm air behaves in the presence of cold air as the balloon : it is displaced and lifted by the cold air, the result being an ascending stream of warm air, which is called a convection current. The movement of ascending smoke is essentially