The ladder having two poles connected by cross rungs is undoubtedly a native invention, and was probably developed through a series of improvements on the primitive notched type. It is described in detail in the earliest Spanish accounts. Fig. 47 illustrates on the left the notched ladder, and on the right a typical two-pole ladder in its most primitive form. In this case the rungs are simply lashed to the uprights. The center ladder of the diagram is a Mandan device illustrated by Mr. Lewis H. Morgan.[6] As used by the Mandans this ladder is placed with its forked end on the ground, the reverse of the Pueblo practice. It will readily be seen, on comparing these examples, that an elongation of the fork which occurs as a constant accompaniment of the notched ladder might eventually suggest a construction similar to that of the Mandan ladder reversed. The function of the fork on the notched ladder in steadying it when placed against the wall would be more effectually performed by enlarging this feature. [Footnote 6: Cont. to N.A. Ethn., vol. 4, Houses and House life, pp. 129-131.] [Illustration: Plate LXXVII. Outline plan of Zuñi, showing distribution of oblique openings.] At one stage in the development of the form of ladder in common use to-day the rungs were laid in depressions or notches of the vertical poles, resembling the larger notches of the single ladder, and then lashed on with thongs of rawhide or with other materials. Later, when the use of iron became known, holes were burned through the side poles. This is the nearly universal practice to-day, though some of the more skillful pueblo carpenters manage to chisel out rectangular holes. The piercing of the side poles, particularly prevalent in Zuni, has brought about a curious departure from the ancient practice of removing the ladder in times of threatened danger. Long rungs are loosely slipped into the holes in the side pieces, and the security formerly gained by taking up the entire ladder is now obtained, partially at least, by the removal of the rungs. The boring of the side pieces and the employment of loose rungs seriously interferes with the stability of the structure, as means must be provided to prevent the spreading apart of the side pieces. The Zuni architect has met this difficulty by prolonging the poles of the ladder and attaching a cross piece near their upper ends to hold them together. As a rule this cross piece is provided with a hole near each end into which the tapering extremities of the poles are inserted. From their high position near the extremities of the ladders, seen in silhouette against the sky, they form peculiarly striking features of Zuni. They are frequently decorated with rude carvings of terraced notches. Examples of this device may be seen in the views of Zuni, and several typical specimens are illustrated in detail in Pl. XCVIII. The use of cross pieces on ladders emerging from roof openings