STEAM. Water converted into steam oc cupies more than 1700 times its former space. Steam will be produced at a proportionally lower temperature if we diminish the pressure of the atmosphere on the water, which may be done either by ascending a mountain or by drawing away a portion of the air by means of an air-pump. When we continue to apply heat to ordinary steam, under a constant bulk, its elasticity rapidly increases, and it is then termed high-pressure; steam of the ordinary temperature being termed low-pressure.
The following table gives the temperature of boiling water and the corresponding pres sures of the air, measured in inches of baro metrical pressure.
Steam has lately been employed in a con siderable number of novel modes, as an effective agent in the arts. A remarkable ' employment of steam in charcoal making is noticed under CntAitcos.L. M. Violette, in a
paper communicated to the Academy of Sci ences in 1848, states that bread and biscuits may be well baked by means of a current of steam at a temperature of about 400° Fahren heit. He also thinks that the cooking of meat may be effected by the same agent. The extraction of wood vinegar (pyroligneous is another process which seems to come within the same range; and as the temperature of the steam, and consequently the heat of the whole process, may be regulated at pleasure, it is thought that the acid may be extracted without the empyreumatic oil which usually accompanies it in the ordinary process. The extraction of wood alcohol (pyroxylic spirit) is attainable by the same means. The drying of wood by highly-heated steam adds another to the list of proposed uses.