Use is made of geometrical constructions to demonstrate the conditions under which a plot ofV/&pgr;R3against ½pRgives a unique curve independent of the value ofR,and also to show how account can be taken of discrepancies due to modified flow near the wall of the tube. In a similar way, the reasoning from which the velocity gradientGWat the wall of the tube can be deduced from experimental figures forV, pandRhas been set out in a geometrical form, which should be helpful to those to whom a pictorial representation makes a ready appeal. The deductions, though simple, involve no loss of generality. The data of Farrow, Lowe and Neale for two percent starch paste are considered by way of example, and it is shown that their formGW=(V/&pgr;R3)(N+3)  where  N=d (logV)/d (logp)of the equation for the velocity gradient at the wall has special advantages. Later work, by disclosing a wider basis, has shown thatNneed not be constant as they supposed, and also that, where modified flow occurs near the wall of the tube,V/&pgr;R3becomesV&bgr;/&pgr;R3, the limiting value for large radii.