It is not surprising that many spurious works were attributed to Aristotle in the middle ages, when we remember that his writings came to them for the most part indirectly through corrupt translations, and that some writing from so great a master was eagerly looked for upon every subject in which they were interested. It seemed to them that so encyclopedic a genius must have touched on all fields of knowledge and they often failed to realize that in Aristotle’s time the departments of learning had been somewhat different from their own and that new interests and doctrine had developed since then. There was also a tendency to ascribe to Aristotle any work of unknown or uncertain authorship. At the close of the twelfth century Alexander Neckam[757] lists among historic instances of envy Aristotle’s holding back from posterity certain of his most subtle writings, which he ordered should be buried with him. At the same time he so guarded the place of his sepulcher, whether by some force of nature or power of art or prodigy of magic is uncertain, that no one has yet been able to approach it, although some think that Antichrist will be able to inspect these books when he comes. Roger Bacon in the thirteenth century believed that Aristotle had written over a thousand works and complained bitterly because certain treatises, which were probably really apocryphal, had not been translated into Latin.[758] Indeed, some of the works ascribed to Aristotle in the Oriental and Mohammedan worlds were never translated into Latin, such as the astrological _De impressionibus coelestibus_ which Bacon mentions, or the Syriac text which K. Ahrens edited in 1892 with a German translation as “Das Buch der Naturgegenstände”; or first appeared in Latin guise after the invention of printing, as was the case with the so-called _Theology_ of Aristotle,[759] a work which was little more than a series of extracts from the _Enneads_ of Plotinus.[760] Some treatises attributed to Aristotle in medieval Latin do not bear especially upon our investigation, such as _Grammar_ which Grosseteste is said to have translated from Greek.[761] [Sidenote: Aristotle and experiment.] For our purposes the Pseudo-Aristotelian writings may be sub-divided under seven heads: experiment, alchemy, astrology, spirits, occult virtues of stones and herbs, chiromancy and physiognomy, and last the famous _Secret of Secrets_. Under the first of these heads may be put a treatise on the conduct of waters, which consists of a series of experiments in siphoning and the like illustrated in the manuscript by lettered and colored figures and diagrams.[762] In a Vatican manuscript it is perhaps more correctly ascribed to Philo of Byzantium. [Sidenote: Aristotle and alchemy: _Meteorology_ and _On colors_.]