There is considerable difference of opinion as to the chronology of the succeeding beds, and the boundary between the Cretaceous and Tertiary systems is drawn at various horizons by different observers.
The igneous rocks occur at several geological horizons, but the great volcanic eruptions did not begin until the Tertiary period.
Hatcher, demonstrate the Pleistocene nature of the deposits, by which is not necessarily meant older Quaternary, for their horizons have not been differentiated and correlated in South America.
Phosphatic nodules and concretions, with phosphatized fossils and their casts, occur at various geological horizons in Great Britain.
Bach's sonatas; then the medium itself began to suggest wider horizons and new possibilities of treatment; his position at Eisenstadt enabled him to experiment without reserve; his genius, essentially symphonic in character, found its true outlet in the opportunities of pure musical structure.