WILLIS] TIEERA COCIDA; SCORIA 49 



Dehydration by slow chemical change produces a red mass, which 

 may grade by color variation into the brown loess, simulating the 

 effect of heat. But the red earth thus produced is not hard like 

 brick. The occurrence observed 8 kilometers north of Miramar is a 

 case in point. If an unquestionably burnt earth should occur in 

 place in the Pampean in a notable mass, it would be necessary to 

 prove that man gathered the fuel and maintained the fire, for the 

 accidental burning of matted vegetation buried in the earth would 

 produce the same effect. The hills of Dakota and Montana in the 

 western United States are banded by red clays burnt to the consist- 

 ency of tile by the combustion of lignite beds, without the agency 

 of man, and what occurs in that region on an extensive scale may 

 well have taken place on the pampas from the combustion of matted 

 masses of grass. 



The specimens of tierra cocida and scoria collected by the writer 

 and Doctor Hrdlicka have been submitted to the Geophysical Labo- 

 ratory of the Carnegie Institution of Wasliington for an exhaustive 

 investigation of their physical characters and conditions of origin, 

 which Mr. F. E. Wright of that laboratory has kindly agreed to make. 

 His report on the subject will doubtless form the basis for further 

 discussion. 



Notes by Ales Hrdlicka 



The writer has recorded a number of personal observations on the 

 subject of the tierra cocida which will serve to supplement the 

 preceding. 



The present coast of the Province of Buenos Aires, north of Baliia 

 Blanca, is devoid of forests, and very poor in wood of any kind, nor 

 are there any indications that it was more favored in this respect at 

 any time during the formation of the Pampean deposits. In conse- 

 quence it is probable that there has been always a dearth of fuel. 

 Tliis doubtless led to the habit, common in the region to this day, of 

 making fire, where it could be made at all, in small, usually quadran- 

 gular excavations in the ground, about 4 to 8 inches deep. A number 

 of these holes were examined by the writer. The ground lining the 

 hole was generally found blackened, and where the heat had been 

 more intense, there was some reddening of the earth beyond the black- 

 ened surface; but both the blackened and the reddened soil (where the 

 latter existed) crumbled readily in every instance, showing but little, 

 if any, cohesion. Nothing was found even remotely resembling Pam- 

 pean tierra cocida specimens thought by some to demonstrate the 

 presence of man. In one instance, at the Laguna de los Padres, some 

 miles inland from Mar del Plata, the remnants of two particularly large 

 21535°— Bull. 52—12 4 



