Atmosphere : a philosophical work / by George Woodhead.

  • Woodhead, George.
Date:
1852
Catalogue details

Licence: Public Domain Mark

Credit: Atmosphere : a philosophical work / by George Woodhead. Source: Wellcome Collection.

    19/164 page 7
    o'lass, whether it be the burning of a piece of wood, or the melting of a piece of iron, both light and air contribute. We know that these agents are both present in the operation; and we do not know that any other agent is present; and in the absence of either of them, the burning-glass will not bm-n. If a light from a lens which sets substances on fire be throwTi into the same substances in an exhausted receiver,* it * Atmospheric air is a fluid which, like water, can be acted upon by mechanical means. By means of air- pumps, air can be drawn out of or forced into any place or space as efiectually as water. To exhaust the air from any particular place or space, it is necessary to suiTound or enclose it with a case or covering of some .sohd substance, such as a glass jar or cup, to keep out the surrounding atmosphere ; and then to draw out the air by an air-pump. An exhausting air-pump is a hollow cylinder of metal, generally brass, with a well- adapted piston, having two valves, one at the bottom of the cylinder, the other in the piston; and the cylinder is connected by a tube, proceeding from its lower or valve end, with a very smooth brass plate, through which it passes and opens on the upper side ; on which, over the orifice, the receiver to be exhausted is
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