WARMING AND VENTILATION. 



28y 



FIG. 21. 



These are all ventilated by means of a large central chimney, 7 feet 

 in inside diameter and 118 feet high, vrhich receives the hot air from the 

 fnrnoces of the steam-boilers, and, when needed, additional heat from 

 a separate firo. ^long the outer face of the side-walls of each building 

 extends a subterranean passage-way of masonry, (cc, Figs. 21, 22,) 2 



feet square, leading to the 

 ft^^^ base of the chimney. Wher- 



ever the phosphorus is 

 placed, an opening is made 

 either in the walls or in the 

 floor, communicating by a 

 small pipe with the under- 

 ground passage so as to 

 carry off the injurious va- 

 pors without allowing them 

 to spread in the shop. 

 Special arrangements differ according to the nature of the work. 

 Thus, where the tips are prepared, a wide and shallow funnel is used, in 



which the draught is increased 

 by the flames of the melting-fire. 

 The shop for the dipping and 

 drying operations, which are the 

 most dangerous, is particularly 

 well ventilated. The general 

 arrangement is shown in the 

 two figures, (21, 22.) The build- 

 ing is GG feet by 49 feet. Along 

 the two sides are placed the dry- 

 ing-chambers E E E, 18 in num- 

 ber, each being G feet wide, IG 

 feet deep, and 7 feet high to the 

 spring of the ceiling-arch, and 9 

 feet to the crown. They are con- 

 nected with the ventilating-tun- 

 nel c c by a triple row of open- 

 ings, o, 0,0, 10 inchesby 5 inches, 

 at the floor-level, and receive 

 the external air either by chimneys extending above the roof or by 

 openings, 9 inches by G inches, placed at the bottom of the iron doors of 

 the drying-rooms, and taking air from the main hall. The doors are G 

 feet high and nearly 3 feet wide. The drying-rooms are heated by three 

 rows of 2-inch steam-inpes placed under the floor. The channels in 

 which these jjipes are placed should receive cold air to be carried 

 directl}' into the drying-chambers. Valves Avorked from the outside 

 of the chambers control the admission and removal of air, which should 

 enter with a temperature of about ]10°, that of the chamber not cxceed- 

 ino- 95^. 



