In a recent publication Thelen described experiments in which the standard penetrometer was used to determine the flow‐shear diagrams for a number of asphalts. On the basis of these diagrams Thelen calculated viscosities which are of different magnitude from those expected from Saal's formula. In the present paper certain fallacies in Thelen's deductions are pointed out. A new method for analyzing Thelen's experimental results is shown which makes it possible to calculate absolute viscosities from penetration readings for a series of successive time intervals. The method is based upon the determination of viscosity by axial displacement of concentric vertical cylinders. Since the conditions under which viscosity can be determined by axial displacement are only approximated in the penetration test the new method cannot be expected to have a high degree of accuracy. Nevertheless from successive penetration readings on a coal tar pitch (penetration 100 g, 5 sec. at 25°C) an average viscosity of 383,000 poises was calculated which closely agrees with the value of 380,000 determined by a capillary rise viscometer. The viscosity as calculated from the initial penetration reading by the Saal formula was 355,000 poises.