Berliner, worked with the phonautograph in the course of developing his own device. Paleophone Charles Cros, a French poet and amateur scientist, is the first person known to have made the conceptual leap from recording sound as a traced line to the theoretical possibility of reproducing the sound from the tracing and then to devising a definite method for accomplishing the reproduction. On April 30, 1877, he deposited a sealed envelope containing a summary of his ideas with the French Academy of Sciences, a standard procedure used by scientists and inventors to establish priority of conception of unpublished ideas in the event of any later dispute. An account of his invention was published on October 10, 1877, by which date Cros had devised a more direct procedure: the recording stylus could scribe its tracing through a thin coating of acid-resistant material on a metal surface and the surface could then be etched in an acid bath, producing the desired groove without the complication of an intermediate photographic procedure. The author of this article called the device a , but Cros himself favored the word , sometimes rendered in French as ('voice of the past'). Cros was a poet of meager means, not in a position to pay a machinist to build a working model, and largely content to bequeath his ideas to the public domain free of charge and let others reduce them to practice, but after the earliest reports of Edison's presumably independent invention crossed the Atlantic he had his sealed letter of April 30 opened and read at the December 3, 1877 meeting of the French Academy of Sciences, claiming due scientific credit for priority of conception. Throughout the first decade (1890–1900) of commercial production of the earliest crude disc records, the direct acid-etch method first invented by Cros was used to create the metal master discs, but Cros was not around to claim any credit or to witness the humble beginnings of the eventually rich phonographic library he had foreseen. He had died in 1888 at the age of 45. The early phonographs Thomas Edison conceived the principle of recording and reproducing sound between May and July 1877 as a byproduct of his efforts to "play back" recorded telegraph messages and to automate speech sounds for transmission by telephone. His first experiments were with waxed paper. He announced his invention of the first phonograph, a device for