. Bulletin - United States National Museum. Science. ^d!!^i â /â ?/â â¢'' » ' â 'â¢â ⢠» \ <- I'm. G^-v^ ^?;ai= to lis in the archaic Castilian of the Alfonsinc Libros del ; The sectifjns of this booi\. dealing with the Laminas de las I'll I'latuias. describe not (jnly this inslriinienl but also the inijiroved modification intro- duced by Azarchicl (born ca. 1029, died ca. 1087). Xo Islamic examples of the equatorium have sur- \i\ed, but iVom this period onward, there appears to Figure 13.â.'\'\be Clock, Regulated by a Mercury Drum, from the Alfonsine Libros del
. Bulletin - United States National Museum. Science. ^d!!^i â /â ?/â â¢'' » ' â 'â¢â ⢠» \ <- I'm. G^-v^ ^?;ai= to lis in the archaic Castilian of the Alfonsinc Libros del ; The sectifjns of this booi\. dealing with the Laminas de las I'll I'latuias. describe not (jnly this inslriinienl but also the inijiroved modification intro- duced by Azarchicl (born ca. 1029, died ca. 1087). Xo Islamic examples of the equatorium have sur- \i\ed, but iVom this period onward, there appears to Figure 13.â.'\'\be Clock, Regulated by a Mercury Drum, from the Alfonsine Libros del saber (see footnote 22). / much easier to mark out "jt'ometrically {, 10, 48, 60, and 64 teeth). The lunar phase volvelle can be seen through the circular o))ening at the Ijack of the astrolabe. It is quite certain that no automatic action is intended: when the central pivot is turned, by hand, probably l)y 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 instru- ment, in practice a turn corresponds more nearly to an interval of one week. 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 Ptole- maic 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 by Abulcacim Abna- cahm {ca. 1025) in Granada; it has been handed down ha\e 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 o
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Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
