product of a certain type of engraving process, 1853, from helio- + -graph "something written." Earlier, "a description of the sun" (1706, implied in heliographic). Heliography (1845 in the engraving sense) also (1840) was an early term for what came to be called photography.
实用例句
1. The heliograph must thus be carefully aligned in the first instance.
