. A treatise on hygiene and public health . traction, requires a system ofducts or flues for the air, andthe rules for the size and pro-portions of such ducts are similarin either case. The primary ducts, or thoseconnecting with the room, aresmaller, and therefore a lowervelocity of the air in them issuitable. The union of severalducts forms a larger one (second-ary duct), in which the air may move more rapidly without needless wasteof force by friction. In the draught-chimney, to which all converge, therate may be greater still. These velocities, beginning with that of a foot i^^^i^^^; 714 TH
. A treatise on hygiene and public health . traction, requires a system ofducts or flues for the air, andthe rules for the size and pro-portions of such ducts are similarin either case. The primary ducts, or thoseconnecting with the room, aresmaller, and therefore a lowervelocity of the air in them issuitable. The union of severalducts forms a larger one (second-ary duct), in which the air may move more rapidly without needless wasteof force by friction. In the draught-chimney, to which all converge, therate may be greater still. These velocities, beginning with that of a foot i^^^i^^^; 714 THE ATMOSPHEEE. and a half or two feet, at the openings from the rooms, are graduated upto seven feet per second (say 2 metres) in the drauglit-chimney. The size of the flues and chimney is naturally dependent upon theamount of air to be drawn through them and the velocity. If we wishto extract ten feet per second from a room, and have allowed a velocityof two feet per second at the registers, we require five registers, each afoot square. Th
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Keywords: ., bookcentury1800, bookdecade1870, booksubjecthygiene, bookyear1879
