The Mohammedan, if he build a mosque, locates it so that its axis extends in the direction of Mecca; in such buildings the mihrab is not necessary, as the natural position of the worshipper places him so that his face is toward the sacred city. Where Christian buildings, such as the great Basilica of St. Sophia at Constantinople have been appropriated for Moslem worship, the niche or mihrab may be located well toward one corner of the building. [Illustration: OLD KIRMAN PRAYER RUG SIZE, 6 × 4.1 _This beautiful and rare rug has an ivory field thickly studded with small floral designs woven most carefully. The knots are very closely tied, and the texture is soft and fine as velvet. A cypress tree occupies the centre of the field, and above its base on either side appears the head of a bird. Below there are two peacocks, in gorgeous plumage. The upper parts of the bodies of the peacocks seem actually to glisten like cloth-of-gold; silk threads appear in the tail feathers. At the top of the rug rests a bird of brilliant plumage, and on either side a bird evidently in the act of flying. The border of this fine rug is in stripes, the widest of a golden hue, with turquoise blue, light green, and soft reds in delicate tracery. The corner areas are deep and very minutely woven, corresponding perfectly with the field. Toward the centre of the corner areas and extending upward, is the mihrab, proclaiming for what purpose this rug was woven._ OWNED BY MISS BUCKINGHAM, CHICAGO.] The prayer rug was evidently invented for the purpose of providing the worshippers with one absolutely clean place on which to offer prayers. It is not lawful for a Moslem to pray on any place not perfectly clean, and unless each one has his own special rug he is not certain that the spot has not been polluted. With regard to the purity of the place of prayer Mohammedans are especially careful when making their pilgrimages, the rugs which they take with them having been preserved from pollution by being rolled up until the journey is begun, or until the hour of prayer arrives. It does not matter to these followers of Mohammed how unclean a rug that is on the floor may be, because over it they place the prayer rug when their devotions begin.