Report on ventilation, 1865.

  • Massachusetts. General Court. House of Representatives. Committee on ventilation of the Representatives' Hall.
Date:
[1865]
Catalogue details

Licence: Public Domain Mark

Credit: Report on ventilation, 1865. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    From this fact we may understand why it is so much more diffi- cult to start a fire in a cold iron fire-pot, than in one of brick, or in one already warm ; for the heat applied to ignite the fuel in the cold iron pot is conducted away so rapidly that the fuel is cooled and the fire may be extinguished. If the walls of the furnace were poor conductors, or already warmed, the heat, instead of being conducted away, would raise the temperature of the fuel and thus cause combustion. When we are seeking to retain heat, we use those substances suited to our purpose, that are poor conductors ; and when we desire to secure the transmission of heat, we use the best conductors. The following table gives the relative conducting power of some ot the most common and ] important substances :- Silver, . 100 Iron,.... . 12 Copper, . 74 Lead, 9 Gold, . . . 53 Platinum, . 8 Brass, . 24 German silver,. 6 Tin, . .15 Bismuth, . 2 The following results of experiments by Count Rumford show the relative rapidity of the conduction of heat through some common substances, valuable for their non-conducting properties:— Twisted silk,. 917 Fine lint, . 1,032 Cotton wool, . . 1,046 Sheep's wool, . . 1,118 Taffety, . . 1,169 Raw silk, . 1,264 Beavers' fur, . . 1,296 Eider down, . 1,305 Hares' fur, . 1,312 Wood ashes, .927 Charcoal, . 937 Lamp black, . 1,117 4. Convection, a property confined to fluids, is the distribu- tion of heat by the transfer of masses of the fluid from place to place. Within the fluid body this property is called diffusion, in contradistinction to conduction, which is the process for the distribution of heat in solid bodies. Though fluids are very poor conductors, large quantities may be warmed very rapidly by taking advantage of the principles which govern their internal motion. When any portion of a liquid is heated, it generally expands, and, becoming lighter, 9
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