TEMPERATURE OF COSSETTES BEING DRIED. 185 



division of the apparatus. They are constantly brought in con- 

 tact with the hot gases, and do not reach the bottom of the 

 dryer until they have become sufficiently light to be carried for- 

 ward by the circulating gases. 



From what has just been said it becomes evident that the 

 cossettes are raised continuously by the revolving agitators until 

 a period when the hot gases will render them sufficiently light 

 to be carried a little farther each time until they reach the ex- 

 terior of the upper trough, from which they fall to the compart- 

 ment directly beneath, always coming in contact with the circu- 

 lating hot gases. They pass through the three divisions of the 

 apparatus and finally fall into the cylindrical trough at the 

 bottom, in which is a revolving spiral that forces the dried resi- 

 duum to the exterior of the apparatus. As the circulating gases 

 always carry a considerable amount of cossettes in suspension, 

 this would mean an ultimate loss; so before leaving the dryer 

 the gases are forced into a "cyclone" where the particles m 

 suspension are deposited, and where they are collected to be 

 subsequently added to the dried cossettes. A special chimney 

 is connected with the dome of the dryer and serves for starting 

 the fire. As soon as this cupola is sufficiently hot, and after 

 the cossettes enter and the exhauster is working, the chimney is 

 closed. As the occasion may demand, this chimney allows the 

 escape of the gases of combustion at a time when the supply of 

 fresh cossettes is less than the practical efficiency of the appa- 

 ratus, due for example to a stoppage in the general working of 

 the factory from which the cossettes are obtained. The cossettes 

 would be burned if some means were not adopted to meet this 

 emergency. Furthermore, it allows, upon occasion, an entrance 

 into the furnace. It permits air to circulate in the dryer when 

 necessary, by which means the gases may be cooled. The 

 apparatus is regulated in such a way that the cossettes, on leav- 

 ing the dryer, are sufficiently desiccated and the gases are suffi- 

 ciently cool to attain their saturation point, without, however, 

 being cooled enough to allow the water to condense. By 

 approaching as nearly as possible this point of condensation, 

 one realizes the economical working of the dryer. 



According to Buttner and Meyer the final temperature in 



