18C0.] Correspondence. 735 preference should be given to American publications, for, as we have said, there is much in English books that is useless here. Winchester, Ya., March 2.j, 1SC9. Dear Sir : — Believing you to be sci- entific as well as practical, and being willing to pay for the information, will 3 r ou please inform me in relation to an idea I have of ventilating. It is to leave openings in the under-side of eaves to let the external air into the spaces be- tween the roof, and finish on the inside; which space will be, in the closest finish, equal to width of rafters and along the sides and top much more : thus giving ample room for horizontal circulation to connect all parts with a flue connected with chimney, or with ventilator in top of roof. This arrangement will cause a draft as the air in said space becomes heated, thus making the attic or upper rooms much more comfortable, and, in case hollow walls are used, there could be a register in walls of each room, j list below the ceiling, connecting with the hollow space — thus allowing the impure to pass into and up through the hollow space in Vails into the hollow space above — thence out at the ventilator or flue; care being had to preserve a good connec- tion. Thus giving a free ventilation to the whole house with but little addi- tional cost. In extreme cold weather the registers for rooms could be closed, or partly so, to prevent the warm air passing out too readily. I am, respectfully, G S . Our correspondent has some excel- lent ideas on the, at present much thought of, subject of ventilation. The method above alluded to is only applicable for summer use, and serves the purposes of the advantage of a cur- rent of air between the ceiling of the upper story and the roof; which of course prevents the usual heating effects of the warm days in summer on the roof, whatever may be the covering material — tin and slate radiating in the. greatest degree. If properly constructed flues from the several rooms of a house be connected, with the air-chamber or duct formed as above stated, and open at or near the ceilings of the other apartments, a thorough draft will be gained, and the air in those apartments will change with a rapidity just in proportion to the degree of heat produced by the sun on the roof. On this the momentum of the current entirely depends. To admit the external air at the eaves will accomplish no more than to have a tendency to free the ceilings of the upper rooms from the penetrating warmth that would naturally be created by a confined volume of heated air. For winter ventilation a directly op- posite course must be pursued. It is then necessary to expel the cold air from the apartments. To accomplish this with the least expense and trouble it is only necessary to construct sepa- rate flues for the purpose, beginning at the bottom of the cellar, say one to each apartment, with a register near the floor. These flues are cold, and the cold air, by its own gravity^ will descend in pro- portion to the volume of warm air, of high temperature, admitted ; and the velocity will be greater in proportion to the degree of coldness of the cold air flues thus constructed. Those cold air flues within the cellar will all be concentrated into one single shaft, to which the gas of the furnace will be admitted. Or, it may be heated by any other means so as to produce the desired effect. [jglF^ We are very willing to receive | criticisms on design or construction, but j we would have it distinctly understood I that no personal allusions will be ad- j mitted to our pages ; neither will we j show favor to an} r communication in 1 which we find an evidence of ungenerous 1 feelinar.
