NATURAL MOUNDS 715 



soil at B, and the line separating them was visible as an approxi- 

 mately straight line entirely across the mound. The material com- 

 posing the mound is essentially like the soil on either side; that is 

 it is reworked clay, probably derived from the underlying subsoil. 



The above section shows clearly that the body of the mound is 

 composed of material exactly like the surrounding soil, which is 

 derived from the underlying clay; and consequently it is a fair 

 inference to suppose that the mound material came from the same 

 source; but, whether this be true or not, the arrangement of the 

 materials proves conclusively that the mound was built, and is not 

 a residual left by erosion or solution. Since in this case the evidence 

 is positive that this mound is not the result of erosion, and also since, 

 in the opinion of the writer, the general evidence against such a 

 mode of origin, at least for the mounds of Arkansas and California, 

 is conclusive, the two hypotheses of erosion and solution, as appKed 

 to the great multitude of mounds in the southern part of the United 

 States, may be dropped. 



The case is now narrowed down to two modes of origin — namely, 

 human construction and the action of burrowing animals. 



Although much has been written regarding the human origin of 

 these mounds, the arguments against it are so strong that it may be 

 classed with the other hypotheses which have been disregarded. 

 It is doubtless true that similar mounds have been erected by pre- 

 historic man, but it is absurd to suppose that the countless millions 

 of mounds which exist in the regions noted above have been the 

 result of human activity. 



This disposes of all the hypotheses, except that which ascribes 

 their origin to the action of burrowing animals; but whether the 

 mounds are due to ants or to small rodents, the writer is unable to 

 say. Personally he incHnes to the ant-hill hypothesis, but there is 

 little or no evidence to determine which is correct. No burrows 

 or chambers of any kind have been discovered in the mounds, and 

 in the case observed by the writer no differences were observed in 

 the character of the underlying clay, which would indicate the former 

 presence of chambers, even though they are now filled. No excava- 

 tions were noted in the neighborhood which could have supplied 

 outside material for the mound, and consequently it is assumed 



