Generally, the problem studied in this dissertation concerns a particular phenomenon encountered in conveying granular solids in gaseous-solids phase horizontal transport. The phenomenon is that at a certain velocity particles will no longer be conveyed, but will settle on the tube bottom forming a layer of stationary solids. Specifically, the goal of this study was to obtain a relationship between the depth of these layers and all the pertinent variables. This relationship was found to be [formula omitted] where: r is the layer depth d is the particle diameter D is the test section pipe diameter g is the local acceleration of gravity W is the solids flow rate/pipe cross-section area Pp is the particle density P is the air density The values or range of values of the pertinent variables for which the above relationship applies is as follows: d 0.032 to 0.201 inches D 2 and 3 inches W 0.68 to 33.3 lb/sec - ft² Pp 15 to 79 lb/cu.ft. P 0.073 lb/cu.ft. Tests were conducted using nearly spherical particles in 100° F, 0.5 psig air. Ambient temperature ranged from 70 - 72° F. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate