THE WARP.âThe appearance of the back of a rug is partly due to the relative positions of the two threads of warp encircled by a knot. If, for instance, in any Kazak a pin be thrust through the nap wherever a single perpendicular line of one colour appears at the surface, it will be seen that each of the two threads of warp encircled by a single knot lie side by side with equal prominence. This is shown in Plate B, Figs. 7 and 7-a (Page 49), in which the former represents a section of a rug cut transversely to the threads of warp, and the latter the appearance of the rug at the back. The same will be found true of Beluchistans, Feraghans, Yuruks, and many others. If, however, a Kulah, Persian-Kurdish, or Karabagh be similarly examined, it will be seen that one thread of warp to each knot is depressed, so that the back has a slightly corrugated appearance (as in Plate B, Figs. 8 and 8-a). And in the case of a Bijar or Sarouk it will be seen that one thread of warp, included in every knot, has been doubled under so as to be entirely concealed from view; with the result that the foundation of warp has a double thickness, which makes the rug much stronger, as in Plate B, Fig. 9, representing a Ghiordes knot, and Fig. 10 representing a Sehna knot. To be sure, it occasionally happens that in rugs of a particular class some may have each thread of warp included in a knot equally prominent and others may have one slightly depressed; or that in rugs of another class some may have one thread of warp depressed and others may have it entirely concealed; but as a rule these tribal features show a remarkable constancy. These relative positions of the two threads of warp encircled by a knot are partly due to the degree of closeness with which the threads of warp are strung, also partly to the method of inserting the threads of weft or "filling" between the rows of knots; but more than all else they are due to the way one end of the knots is pulled when they are tied.
THE WEFT.âIn the character and arrangement of weft are technical differences that are more serviceable than any other feature for distinguishing between the rugs of different tribes and districts. So subtle are some of them that they can be learned only by long and painstaking study, and are appreciated by few except native weavers. Nevertheless, to any one who will carefully examine almost any well-known classes, it will be apparent that these differences in the weave are real, and that they are sufficiently constant to differentiate one class from another. The fine brown weft of the Bokhara, or equally fine bluish weft of a Sarouk that is almost concealed between firmly tied knots; the fine thread of cotton weft passing but once between two rows of knots and covered only by the transverse warp of the Sehna; the coarse thread of cotton weft similarly passing but once between two rows of knots in the Hamadan; the coarse thread of cotton weft that once crossing and recrossing appears irregularly between appressed rows of knots in Kermanshahs; the bead-like appearance of the threads of weft that, as a rule, pass many times between two rows of knots in Genghas; the crudely spun weft of coarse diameter crossing and recrossing once between the rows of knots in modern Mosuls; the very fine reddish brown weft that entirely conceals from view the warp in old Bergamos, âare features peculiar to these separate classes with which every rug expert is familiar. The weft of many other classes is equally distinctive, though there are exceptions to the types. It should be remembered, however, that the weave of many rugs woven over a hundred and fifty years ago is different from the weave of rugs woven only fifty years ago; and that many modern pieces cheaply made for commercial purposes are more crudely woven than were the same classes thirty years ago.