NOTEMBEE 27, 1914] 



SCIENCE 



783 



various hypotheses is compatible with exist- 

 ing facts and conditions, and there is no just 

 or plausible reason why Cahokia should be 

 considered other than the work of man, erected 

 after the Mississippi had reached its present 

 channel. True at some time in the past the 

 waters of the Mississippi reached the foot of 

 the bluffs now forming the eastern boundary 

 of the wide lowland upon which the mounds 

 stand. The waters gradually wore away the 

 western bank of the stream until masses of 

 limestone, now forming the cliffs on the Mis- 

 souri side, were reached. Here a new and 

 permanent channel was formed, and so it has 

 remained until the present time. The entire 

 area between the eastern line of bluffs and the 

 limestone on the west was scoured by the ad- 

 vancing waters, and no single mass of the loose 

 formation could have withstood the elements 

 and thus remained an isolated mound near the 

 center of the plain. The lowland was formed 

 by the gradual shifting of the channel from 

 the east to the west ; this movement continued 

 until it was arrested by the resistant lime- 

 stone. Cahokia stands upon the lowland about 

 midway between the two lines of bluffs. This 

 area was reduced to its present level by ero- 

 sion, during the time the stream was moving 

 from the east and seeking its present bed. 

 Therefore it would have been a physical im- 

 possibility for the mounds, standing at the 

 present time, to have been erected at a time 

 when the waters of the Mississippi flowed along 

 the foot of the bluffs to the eastward. 



Some five years ago Mr. N. M. Fenneman in 

 "Physiography of the St. Louis Area," Bul- 

 letin 12, Illinois State Geological Survey, 

 wrote (p. 63) : 



The partly artificial character of Monks' Mound 

 is evident from its form. That it is in part a 

 natural feature is seen by its structure. Sand is 

 found neatly inter-stratified with loam at an alti- 

 tude of about 455 feet, or 35 feet above its base. 

 To this height, at least, the mound is natural and 

 as there is sufficient other evidence that the val- 

 ley was filled in the Wisconsin epoch to at least 

 that height, the original mound may be regarded 

 as a remnant of the alluvial formation of that 

 time. Its base was probably narrowed artificially 

 by the removal of material which was carried to 



the top. In this way also the conspicuous abrupt- 

 ness of its slopes was probably produced. No nat- 

 ural stratification has yet been found more than 

 35 feet above its base and therefore, for aught 

 that is now known, more than half its height may 

 be artificial. 



The discovery of a mass of sand in the 

 body of the mound does not prove the lower 

 part of the structure to be of natural origin. 

 The sand is mentioned as being " neatly inter- 

 stratified with loam," but no statement ap- 

 pears as to the extent of the stratum. Was it 

 found exposed on all sides of the work or only 

 at one point? Probably the latter. 



Of the great number of artificial mounds 

 which have been examined few; if any, have 

 been a homogeneous mass. Distinct strata of 

 sand, clay, charcoal and ashes, vegetal mold or 

 other materials, occur in the mounds. In some 

 small deposits of clay, of sand and of black 

 soil are in close contact, each mass being the 

 quantity that could have been easily carried 

 by one person. During the construction of the 

 mounds many persons were necessarily engaged. 

 The earth or sand was carried in bags or baskets 

 from the chosen area and gradually the mass 

 accumulated and the mound was formed. If 

 a natural deposit of sand was encountered by 

 the builders on one side of the work, while 

 loam was being carried from another point, 

 the result would be a pocket of sand in the 

 artificial work. This may explain the occur- 

 rence of sand " neatly inter-stratified with 

 loam," as mentioned by Mr. Fenneman. This 

 question will be more clearly understood by 

 referring to the writings of Mr. 0. B. Moore, 

 in which he describes the structure of many 

 mounds excavated by him throughout the 

 southern states, and likewise to the Twelfth 

 Annual Report of the Bureau of Ethnology. 



One illustration in Mr. Fenneman's work 

 deserves mention. Fig. B, PI. 6. This shows 

 three mounds directly south of Cahokia and 

 bears the legend: 



Group of Mounds one half mile south of Monks' 

 Mound. The low grassy knoll at the left is be- 

 lieved to be entirely natural. It suggests the orig- 

 inal forms of the larger mounds which have been 

 artificially shaped. 



