16 



CASEIN. 



drum axis toward the horizontal. Each revolution of the 

 drum, therefore, moves every particle of the contents spirally 

 onward, the rate of advance being regulated by two factors 

 the speed of the drum and the axial slope. If the latter be 

 nil, the pitch of the aforesaid spiral will be also nil, and the 

 material will be turned over but not moved forward ; and in 

 proportion as the axial slope is increased or diminished, so 

 also will the material in the drum move faster or slower. 

 Since the same drum is used for drying different materials 

 at different times, or for treating the same material contain- 

 ing different percentages of moisture, it is advisable to make 



FIG. 6. Eotary Drying Cylinder. . 



provision for working in a corresponding manner, which can 

 be most easily done by making the axial slope adjustable. In 

 this manner the onward movement of the material can be 

 accelerated or retarded as required, and the drying process 

 carried on in a uniform manner at the smallest expense. A 

 few instances of typical drying cylinders will now be given, 

 the details of which can be modified according to require- 

 ments. 



Fig. 6 represents a horizontal drum (a) fitted with a shaft 

 (6), the arms (c) of which move the material onward. The 

 cylinder is of the fixed type, and is jacketed for steam heat- 



