Measurements of total pressure drop and static pressure drop in t h e transport of solid particles through vertical 0.267and 0.532-inch inside diameter glass tubes by an air stream are reported. Closely sized sand (28t o 35-, 35-to48-,48-t060-, and60-to80-meshTyler),and bothground and spherical silica-alumina cracking catalyst were used. Solids circulation rates ranged from 2 to 54 pounds per second per square foot a t various constant air rates fromConverting to inches of water and substituting G8/uI for p d s ,