MiNDELEFF] CONDITION OF CASA GRANDE IN 1895 349 



Ou examiniug the .structure to ascertain the effect of the i)rotecti\ e 

 works of 1892 in stayiug the destructive processes, particuhirly the 

 uiuleriuiuing of the walls by spattering rain and drifting sand, it was 

 found that in most cases the results have been excellent. Ou the inner 

 side of the middle section of the southern exterior wall sapping is in 

 progress at the ground level, and also along the rows of joist opeuinj.;s 

 for the first and second stories, and in a few other places the protection 

 seems inade(iuate; but in general the anticipations of the projectors of 

 the protective works seem to have been realized. 



The most serious of the destructive i)rocesses was sapping, and this 

 process has been nearly checked by the piotective works. The second 

 was the desurfacing and subsequent eating away of the walls by beat- 

 ing rains and frost, and this is still in progress at a moderate rate. 

 The least serious process was the wearing away of the crests of the 

 walls by rain and winds, and this is still going on at a perceptible rate. 

 It is impossible to determine, and difficult even to approximate, the rate 

 of destruction ([uautitatively.especiallyso since it goes ou cumulatively, 

 with constantly increasing rai)idity, as the cemented surfaces are de- 

 stroyed and the crevices widen and deepen ; but judging from the his- 

 tory of the ruin, and from the rate of destruction indicated bj' comparing 

 the photographs of 189- with tlie present aspect, it would seem safe 

 to conclude that, if protected completely from vandalism, the ruin will 

 be comparatively little injured during the next five years, and will 

 stand perhaps half a cenluiy, without further protective works, before 

 moldering into dust. 



In view of the slow yet ever increasing rate of destruction of the 

 ruin, and of its great interest as a tangible record of the prehistoric 

 inhabitants of this country, no liesitation is felt in recommending that 

 the structure be further protected, and practically perpetuated, by a 

 suitable roof, so designed as to shield the walls from rain and sun and 

 at the same time permit an unobstructed view of the ruin from any 

 direction. 



1 have the honor to be, sir, yours, with great respect, 



J. W. Powell, Director. 

 The Secretary of the Interior. 



