The property of a mud-laden fluid to resist flow due to internal friction and the combined effects of adhesion and cohesion; e.g., a Marsh funnel (used to measure the viscosity of 2077 mud) will discharge 1 quart (0.95 L) of water in about 36 s, whereas an equal volume of an average drilling mud is discharged in 40 to 55 s or more from the same funneI.