AND VISIT TO CASAS GRANDES. = *_- 351. 
ter preservation and support of that portion of the edi- 
fice. By far the larger portions which have fallen are 
the exterior walls. This arises from the moisture of 
the earth and the greater exposure to rains. The cen- 
tral parts are in a measure protected by the accumula- 
tion of rubbish, and by the greater thickness of their 
walls. 
I should observe that every portion of this edifice 
is built of adobe, or mud, and that nowhere, as far as 
T could trace the foundations, could I discover any 
Walls of stone. The point in which it differs from the 
work of the Spaniards or modern Mexicans, is in the 
mode of constructing the walls. The latter employ 
regularly made brick, from fourteen to sixteen inches 
in length, about twelve in width, and three or four in 
thickness, often mixed with chopped straw and gravel, , 
and baked in the sun—a mode adopted ages ago by the 
Primitive inhabitants of Egypt, Assyria, and other 
Oriental countries, and practised by them at the pre- 
sent day. But the buildings of which I now speak 
are built with large blocks of mud, or what the Mexi- 
cans call tapia, about twenty-two inches in thickness, 
and three feet or more in length. In fact, the length 
of these blocks seemed to vary, and their precise 
dimensions could not be traced; which induced me to 
believe that some kind of a case or box was used, into 
Which the mud was placed, and as it dried, these cases 
Were moved along. It is true, they may have been 
first made in moulds or cases, and, after being dried, 
placed on the walls; but the irregularity and want of 
uniformity in these layers as to their length, leads me 
to believe they were made on the walls themselves. 
