WARMING AND VENTILATION 293 



to 1,000 revolutions a second, and requiring at most 8 to 10 4iorse-power 

 to run it, easily removes all the dust produced during the truing of the 

 two main stones and twelve of the grooviug-stones, the other passages 

 being closed. 



The axis of the fan-blower is placed in the line of the last collecting- 

 pipe, and is closed on the side opposite that pipe; the air carrying the 

 dust is expelled at the outer circumference, which is entirely free. 



Notwithstanding the success obtained in large works by the arrange- 

 ments mentioued above, it would be better in all cases to separate the 

 workmen into small shops of two stones each, each furnished with spe- 

 cial ventilating-apparatus similar to that which we have described. 

 Eecent trials seem to show that ventilation obtained by forcing in air 

 would in this case prove very satisfactory. 



DRYING-CHAIVIBEES. 



77. The general arrangements which should be adopted ibr drying- 

 chambers are in conformity with the rules previously given. The air 

 should flow in at the top ; and, as in this case, it is always very hot, it 

 enters of its own accord, but it is necessary that it should be introduced 

 uniformly. The openings for the escape of the air saturated with moist- 

 ure should be placed near the floor and on the whole circumference of 

 the room. It issufiicient to connect the ventilating-pipes with the base 

 of the chimney of the heating-apparatus. 



The temperature which it is necessary to keep up in the drying- 

 chambers depends upon the nature of the articles to be dried. For 

 vegetable substances and flour, it need not exceed 105° or 110° ; for 

 linen and cloth, loS^". 



The particular conditions in each application may lead to some modi- 

 fications of the general rules. Linen-drying rooms present a case which 

 it is well to specify. 



LINEN-DEYING CHAMBERS. 



78. The arrangements for these useful accessories (Figs. 25, 2G) to" 

 large bleaching-establishments have been carefully studied by Bouillon, 

 Muller & Co. The linen is carried to the wringing-machine, which re- 

 moves from it a great part of the water which it contains after having 

 been washed ; but it still retains about one-third of the total weight 

 when it reaches the drying-room. When it is hung vertically, this water 

 accumulates principally at the lower part, which therefore becomes hard 

 to dry. Again, when the air enters through a single opening at the up- 

 per part of the chamber, the interruption to the circulation of hot air 

 caused by the linen which hangs in vertical bands and the force of the 

 draught which tends to draw the air directly" toward the ventilating-opeu- 

 ings prevents the drying from proceeding uniformly, especially in large 

 dry ing-houses. The observation of these irregular efl'ects has led Bouil- 



