  The notion of number line was formed in XX c. We consider the generation of
this conception in works by M. Stiefel (1544), Galilei (1633), Euler (1748),
Lambert (1766), Bolzano (1830-1834), Meray (1869-1872), Cantor (1872), Dedekind
(1872), Heine (1872) and Weierstrass (1861-1885).
