March 31, 1905.] 



SCIENCE. 



515 



some parts of the drift-covered portions of the 

 region south of Puget Sound. 



The theories usually advanced in explana- 

 tion of these mounds on the Pacific coast are: 

 (1) Surface erosion, (2) glacial origin, (3) 

 teolian origin, (4) human origin, (5) burrow- 

 ing animals, including ants, (6) fish-nests ex- 

 posed by elevation. 



Bearing upon the theory of ant origin men- 

 tioned by Mr. Veatch, something will be found 

 in the Bulletin of the Geological Society of 

 America, Vol. VII., pp. 295-300, and also in 

 the Journal of Geology, VIII., 151-153. It 

 ought to be noted, however, that the ant-hills 

 of the tropics with which I am acquainted, 

 remarkable and abundant as they are, do not 

 much resemble the hog-wallows or i^rairie 

 mounds. Perhaps, however, no great stress 

 can be placed upon this difference. The ant- 

 hills of Brazil vary greatly in size and form, 

 according to the species building them and ac- 

 cording to the soil. If it be assumed that the 

 ants built the mounds in this country and 

 disappeared long ago, it is to be expected that 

 time would have greatly modified and toned 

 down their original relief. It is, perhaps, 

 worthy of note, and may be of interest in 

 connection with the ant-hill theory, that in 

 western Washington and in parts of California 

 they are partly on glacial soils, that is, on 

 drift or on sediments spread over the San 

 Joaquin valley during the glacial epoch. The 

 glacial theory of their origin suggested by the 

 letter of "Wallace in Natwe, XV., 274, is with- 

 out support — the glaciers in California did not 

 reach the region of the hog-wallows in the 

 San Joaquin valley. 



In addition to what Mr. Veatch says of the 

 distribution of the mounds in the Mississippi 

 valley it may be stated that they follow up 

 the valley of the Arkansas and of the Neosho 

 rivers across Indian Territory into southeast- 

 ern Kansas. In Arkansas and Indian Terri- 

 tory they are common in forests as well as in 

 prairies. 



It is supposed that sections through these 

 mounds would explain them. In California 

 hundreds of mounds have been cut through by 

 railways and by common roads, and many 

 such sections have been examined. The cut- 



tings, being made without any special care, 

 exhibit only a compact clayey ' hard-pan ' that 

 shows no signs of burrows or anything that 

 has been recognized thus far as different from 

 the soil of the adjacent areas. In the San 

 Joaquin valley the soil of the hog-wallows is 

 not regarded as good. In some places it is so 

 hard that it is very difficult to plow it. In 

 the region between the San Joaquin Eiver 

 and the city of Fresno the soil of these hog- 

 wallows is mostly of quartz, feldspar, mica 

 and hornblende, with a little clay and some 

 iron. These materials are derived from the 

 granites and other crystalline rocks of the 

 mountains to the east. One section examined 

 in a pit eight feet deep and one thousand feet 

 north of Herndon station is spoken of in my 

 notes as a ' hard-pan of quartz sand, clay and 

 feldspar resembling a horizontally bedded 

 sandstone with some clay in it.' 



Similar mounds occur in many places and 

 covering large areas over the flat prairie lands 

 along the eastern slopes of the Andes in the 

 Argentine Kepublic. I used to think the 

 Argentine mounds were of asolian origin, but 

 while some mounds are evidently made in this 

 way, the explanation is not satisfactory for 

 the great bulk of them. 



Of the theories spoken of above, the ant- 

 hill theory seems to me the most plausible, 

 but with our present knowledge it is far from 

 satisfactory. One other theory has been in 

 my own mind for several years, but it is al- 

 most entirely without observations to support 

 it, and it is, perhaps, too vague to be clearly 

 expressed. The idea is that in soils of certain 

 kinds long exposed to weathering agencies 

 chemical reactions possibly take place around 

 centers that result in the transfer of minerals 

 in solution to and the precipitation in nuclei 

 that are now represented by the positions of 

 the mounds, while the withdrawal of these 

 minerals from the intervening areas causesi 

 the depressions around the mounds. In other 

 words, it is a theory of concretionary action 

 on a large scale due in part to chemical and 

 in part to physical conditions. With this the- 

 ory in view I have gathered samples from 

 beneath the hog-wallows laear Fresno and 

 others will be gathered during the coming 



