Roger Bacon speculates about such things as gunpowder, flying machines, telescopes, and mechanically driven carriages.

Bacon is often considered the first European to describe a mixture containing the essential ingredients of gunpowder.

Based on two passages from Bacon's Opus Majus and Opus Tertium, extensively analyzed by J. R. Partington, several scholars cited by Joseph Needham concluded that Bacon had most likely witnessed at least one demonstration of Chinese firecrackers, possibly obtained with the intermediation of other Franciscans, like his friend William of Rubruck, who had visited the Mongols.

With the death of Pope Clement died in 1268, Bacon had lost his protector.

Suspected of promoting "dangerous novelties," he is apparently imprisoned or placed under house arrest for two years, probably between 1277 and 1279, by order of the minister-general of the Franciscans, as punishment for his excessive credulity in alchemy and for his harsh regard for the other innovators of his time.

Bacon some time after 1278 returns to the Franciscan House at Oxford, where he continues his studies.