Field evidence about the viscosity of lavas

There appears to be surprisingly little definite information on the viscosity of lavas. With few exceptions writers content themselves with such general and indefinite terms as “mobile”, “viscous”, or “highly viscous”. Apparently the only attempts to actually calculate viscosity have been made on Hawaiian lavas. G. F. Beoker (Some queries on rook differentiation, Amer. J. Sci., 4th ser., v. 3, pp. 27–32, 1927) basing his calculations on the record of the 1840 flow at Kilauea which progressed eleven miles down a two per cent slope in two days, concluded that this lava had a viscosity about 60 times that of water.