This landmark in the history of science and technology is now preserved at the Museum of the History of Science, Oxford, England.[21] It is an astrolabe, dated 1221-22 and signed by the maker, Muḥammad b. Abī Bakr (died 1231-32) of Isfahan, Persia (see figs. 11 and 12). The very close resemblance to the design of Biruni is quite apparent, though the gearing has been simplified very cleverly so that only one wheel has an odd number of teeth (13), the rest being much easier to mark out geometrically (_e.g._, 10, 48, 60, and 64 teeth). The lunar phase volvelle can be seen through the circular opening at the back of the astrolabe. It is quite certain that no automatic action is intended; when the central pivot is turned, by hand, probably by using the astrolabe rete as a "handle," the calendrical circles and the lunar phase are moved accordingly. Using one turn for a day would be too slow for useful re-setting of the instrument, in practice a turn corresponds more nearly to an interval of one week. [Illustration: Figure 13.--ASTROLABE CLOCK, REGULATED BY A MERCURY DRUM, from the Alfonsine _Libros del saber_ (see footnote 22).] In addition to this geared development of the astrolabe, the same period in Islam brought forth a new device, the equatorium, a mechanical model designed to simulate the geometrical constructions used for finding the positions of the planets in Ptolemaic astronomy. The method may have originated already in classical times, a simple device being described by Proclus Diadochus (_ca._ 450), but the first general, though crude, planetary equatorium seems to have been described by Abulcacim Abnacahm (_ca._ 1025) in Granada; it has been handed down to us in the archaic Castilian of the Alfonsine _Libros del saber_.[22] The sections of this book, dealing with the _Laminas de las VII Planetas_, describe not only this instrument but also the improved modification introduced by Azarchiel (born _ca._ 1029, died _ca._ 1087). No Islamic examples of the equatorium have survived, but from this period onward, there appears to have been a long and active tradition of them, and ultimately they were transmitted to the West, along with the rest of the Alfonsine corpus. More important for our argument is that they were the basis for the mechanized astronomical models of Richard of Wallingford (_ca._ 1320) and probably others, and for the already mentioned great astronomical clock of de Dondi. In fact, the complicated gearwork and dials of de Dondi's clock constitute a series of equatoria, mechanized in just the same way as the calendrical device described by Biruni.