The two-term friction law is presented in a form following from its de
rivation on the basis of the effect of molecular forces close to the s
hort- and long-range forces. This proves its heuristic significance. T
he boundary friction mechanism is described, in particular that applic
able to the theory of sliding on ice. This theory was substantiated st
rictly quantitatively. In conclusion, the problem is formulated on the
side of the transition from the viscous mode of a lubricating layer t
o the boundary lubrication mode.