answer any question. The story appears in the anonymous 16th-century account of The Famous Historie of Fryer Bacon, in which Bacon speaks with a demon but causes the head to speak by "the continuall fume of the six hottest Simples", testing his theory that speech is caused by "an effusion of vapors". Around 1589, Robert Greene adapted the story for the stage as The Honorable Historie of Frier Bacon and Frier Bongay, one of the most successful Elizabethan comedies. As late as the 1640s, Thomas Browne was still complaining that "Every ear is filled with the story of Frier Bacon, that made a brazen head to speak these words, Time is". Greene's Bacon spent seven years creating a brass head that would speak "strange and uncouth aphorisms" to enable him to encircle Britain with a wall of brass that would make it impossible to conquer. Unlike his source material, Greene does not cause his head to operate by natural forces but by "nigromantic charms" and "the enchanting forces of the devil": i.e., by entrapping a dead spirit or hobgoblin. Bacon collapses, exhausted, just before his device comes to life and announces "Time is", "Time was", and "Time is Past" before being destroyed in spectacular fashion: the stage direction instructs that "a lightening flasheth forth, and a hand appears that breaketh down the Head with a hammer". A necromantic head was ascribed to Pope Sylvester II as early as the 1120s, but Browne considered the legend to be a misunderstanding of a passage in Peter the Good's Precious Pearl where the negligent alchemist misses the birth of his creation and loses it forever. The story may also preserve the work by Bacon and his contemporaries to construct clockwork armillary spheres. Bacon had praised a "self-activated working model of the heavens" as "the greatest of all things which have been devised". As early as the 16th century, natural philosophers such as Bruno, Dee and Francis Bacon were attempting to rehabilitate Bacon's reputation and to portray him as a scientific pioneer who had avoided the petty bickering of his contemporaries to attempt a rational understanding of nature. By the 19th century, commenters following Whewell considered that "Bacon... was not appreciated in his age because he was so completely in advance of it; he is a 16th- or 17th-century philosopher, whose lot has been by some accident cast in the 13th century". His assertions