English translation of title: "On the Cause of the Earth's Remaining in Its Position (in the Middle of the Heavens)". Written in Gurganj (ca. 1005-12)for Abū al-Ḥasan Aḥmad b. Muḥammad al-Sahlī. Same work listed by Ibn Abī `Uṣaybi`a (and in the "longer list" (Gohlman, pp. 102-3 (no. 44)) as Maqāla fī hay’at al-arḍ min al-samā’ wa-kawnihā fī al-wasaṭ [Ragep and Ragep 2004]; Other references: GAS VI, p. 279 (4) ; MAMS v2.231 (A6); Mahdawi, pp. 181-182 (no. 91); printed in Kurdī  [1917], pp. 152-64.