The destructive power of intruding magmas is sometimes overstated as a consequence of the belief that high drag force is automatically the result of high viscosity, or because a magma contains phenocrysts or xenoliths which cause abrasion. However, consideration of the principles of fluid dynamics indicates that the opposite may generally be the case. Abrasion by particles suspended in a viscous magma is negligible, and the drag forces associated with viscous flow are not necessarily large inasmuch as high viscosity acts to limit flow rate. These contentions are demonstrated analytically for the aqueous suspension model of the formation of orbicules and comb layering proposed by Moore and Lockwood, for which the effects of an aqueous fluid and magma may be compared. As a result of this analysis, a magmatic origin for comb layering and orbicle growth is preferred, a conclusion compatible with other interpretations of comb layering.