BOLE).
The optical extinction angles in the plane of symmetry are usually smaller than those of the corresponding pyroxenes. Horn blende is an essential constituent of many igneous and metamor phic rocks, being specially prominent in diorites, amphibolites and hornblende-schists. Exceptionally well-crystallized examples are known from the basalts of Bilin and Schima (Czechoslovakia).
a name originally applied to a sheet contain ing the letters of the alphabet, which formed a primer for the use of children. It was mounted on wood and protected with transparent horn. The wooden frame had a handle, and it was usually hung at the child's girdle. The sheet, which in ancient times was of vellum and latterly of paper, contained first a large cross—the criss-cross—from which the horn-book was called the Christ Cross row, or criss-cross-row. The alphabet in large and small letters followed. The vowels then formed a line, and their combinations with the consonants were given in a tabular form. The usual exorcism—"in the name of the Father and of the Sonne and of the Holy Ghost, Amen"—followed, then the Lord's Prayer, the whole concluding with the Roman numerals.