REPOET OF THE SECRETARY. 55 



there was once a great Tertiary lake, wliicli was gradually filled witli 

 the sauds washed into it on every hand and by the ashes blown out of 

 the adjacent volcanoes. Tbis great lake formation is in some places a 

 thousand feet in thickness. When the lake was filled, the Rio Grande 

 cut its channel through the midst to a depth of many hundreds of feet. 

 The volcanic mountains to the westward send to the Eio Grande a 

 number of minor streams, which in a general way are parallel with one 

 another. The Eio Grande itself and all of these lateral streams have 

 cut deep gorges and caSons, so that there are long, irregular table Lnids, 

 or mesas, extending from the Eio Grande back to the Valley Mountains, 

 each mesa being severed from the adjacent one hy a canon oi- canon 

 valley; and each of these long mesas rises with a precipitous cliff from 

 the valley below. The cliffs themselves are built of volcanic sands and 

 ashes, and many of the strata are exceedingly light and friable. The 

 specific gravity of some of these rocks is so low that they will float on 

 water. Into the faces of these cliffs, in the friable and easily- worked 

 rock, many chambers have been excavated; for mile after mile the clitfs 

 are studded with them, so that altogether there are many thousnmls. 

 Sometimes a chamber or series of chambers is entered from a terrace, 

 but usually they were excavated many feet above any landing or ter 

 races below, so that they could be reached only by ladders. In other 

 places artificial terraces were built by constructing retaining-walls and 

 filling the interior next to the cliff with loose rock and sand. Very often 

 steps were cut into the face of a cliff and a rude stairway formed by 

 which chambers could be reached. The chambers were very irregularly 

 arranged and very irregular in size and structure. In raauj^ cases there 

 is a central chamber Avhich seems to have been a general living-room 

 for the people, and back of which two, three, or more chambers somewhat 

 smaller are found. The chambers occupied by one family are some- 

 times connected with those occupied by another family, so that two or 

 three or four sets of chambers have interior communication. 



Usually, however, the communication from one system of chambers to 

 another was by the outside. Many of the chambers had evidently been 

 occupied as dwellings. They still contained fire-places and evidences 

 of fire ; there were little caverns or shelves in which various vessels 

 were placed, and many evidences of the handicraft of the people were 

 left in stone, bone, horn, and wood, and in the chambers and about the 

 sides of the cliffs potsherds are abundant. On more careful survey it 

 was found that many chambers had been used as stables for asses, 

 goats, and sheep. Sometimes they had been filled a few inches, or even 

 two or three feet with the excrement of these animals. Ears of corn 

 and corncobs were also found in many places. Some of the chambers 

 were evidently constructed to be used as storehouses or caches for grain. 

 Altogether it is very evident that the cliff houses have been used in 

 comparatively modern times, at any rate since the peoi)le owned asses, 

 goats, and sheep. The rock is of such a friable nature that it will not 



