AbstractPrevious studies of the pipeline movement of single paste slugs of coal have been extended to determine the velocities of, and the pressure gradients along, trains of slugs. The measurements were taken in a 70‐foot long, closed‐loop line made from 0.95‐inch bore, rigid plastic tubing. Flow in the line could be switched to maintain continuous movement of a train of slugs.Tests were made with slugs of 80:20 (w/w) coal‐water paste which was extruded through a 0.775‐inch die and also with slugs which were stabilized by the addition of agar to the water used for making the slugs. Slugs made from coal and agar solution were formed in cylindrical molds having diameters of 0.567, 0.661 and 0.756 inches and were intended to show more clearly the influence of slug diameter on the behavior of the trains. Individual slugs were five inches in length and were formed into trains with lengths of up to fifteen feet for the tests. The oil used as carrier fluid was a light mineral oil (μ = 5.92 cp,σ = 0.826 at 70°F.), which was circulated through the pipeline loop at velocities ranging from 1.0 to 10.0 ft./sec.