PEWKES] NAVAHO NATIONAL MONUMENT, ARIZONA 13 
issuing from almost under the walls and trickling down through the 
bushes over a mass of fallen rock which forms the talus. The climb 
to the ruin from the place where horses must be abandoned is not 
a hard one and a trail could easily be made; in fact a carriage 
road might be constructed at small expense from Marsh pass to 
within half a mile of this great ruin, one of the largest two and 
best preserved cliff-dwellings in the Navaho National Monument. 
A feature of this ruin (plates 8-11) which attracts attention on 
entering it is the fine echo, due to the shape of the open cave in which 
it lies. Were the name not preempted, it would seem that Echo 
House would be a much more appropriate designation for the ruin 
than Betatakin, ‘‘ High-ledges House,” applied to it by the Navaho. 
Certain differences in architectural features between cliff-houses in 
the Mesa Verde region and those here considered are apparent. The 
caves in which the cliff-dwellings of the Navaho Monument region are 
situated differ in geological formation from those of the Mesa Verde 
National Park. While in the former there are many instances of 
horizontal cleavage planes, as a rule the falling of blocks of stone has 
left vertical flat faces. On this account the caves are shallow and 
high-vaulted rather than extending deep into the cliff. The process 
of formation of these vertical planes of cleavage is shown by examining 
plate 9; in this case a pinnacle of rock has begun to break away and is 
partially separated from the surface of the cliff. This pinnacle will 
ultimately topple over and fall as many have done before, leaving a 
broken stump at its former base. In this way, from time to time, in 
the past geological history of the cave, detached pinnacles and slabs 
of rock have broken away along these vertical planes of cleavage, 
leaving the tops of their broken bases later to become foundations 
for rooms. Similar flat vertical planes of cleavage are rare, almost 
unknown, in the Mesa Verde caves. Here the cleavage is horizontal, 
the caves extending deep into the cliffs.“ 
The modifications in architecture brought about by the difference 
in direction of these cleavage planes are apparent. The ancient 
builders in the Navaho Monument region utilized the vertical faces 
as supports for walls of rooms on one or more sides. In some cases 
the face of the cliff forms the rear walls; in others a side wall and the 
rear wall of a room are formed by vertical cleavage planes at right 
angles, as shown in plate 9. It can be seen that adjacent houses built 
upon fallen rocks of different heights, the vertical faces being utilized 
as rear walls, would seem to stand one above another, or, in other 
words, they would present the well-known terrace form which exists 
in some modern pueblos. 
@ Another geological feature of the sites of the large cliff-dwellings of the Navaho Monument is the 
almost constant presence of a vertical cliff-wall below the cave floor, the talus rarely extending to the 
\base of the lowest rooms. 
