Consists of an introduction and 2 chapters (one on hay'a of the celestial region, the other on the hay'a of the Earth. This work is distinct from his "Zubdah-i hay'a" (a short work on hay'a), in Persian. Ṭūsī states in the introduction that his intention is to epitomize the available works on "hay'a." [Ragep 1982, p. 44 (dissertation)] 