August 28, 1896.] 



SCIENCE. 



263 



following a given deptli under the surface, 

 whicli is about three feet, it is evident that 

 the difference in color is due to a modifica- 

 tion of the red clay by some action either 

 atmospheric or aqueous. Now, red clay is 

 the natural residual product of the decay- 

 ing limestone. Red is, also, the color most 

 generally represented in the mud of the 

 caves. Indeed, there is no macroscopic dif- 

 ference between the red cave earth and the 

 clay on the limestone rocks outside. They 

 are due to the same general cause and con- 

 stitute the same formation. But the upper 

 three feet of the residual clay on the ridges 

 has been converted into a yellow clay. The 

 same effect has been observed and recorded, 

 by numerous writers, in other unglaciated 

 districts, but in this it is perhaps more 

 prominent than in others. The cause ap- 

 pears to have been not the action of the 

 atmosphere, which is incapable of destroy- 

 ing and removing the red oxide of iron, but 

 the solution and removal of a large part of 

 the iron salt, by percolating water contain- 

 ing acids generated by the decay of the vege- 

 table matter contained in and on the soil. 

 The writer, believing that certain colors 

 are, to some extent, characteristic of the pro- 

 ducts of certain periods and certain climates, 

 wishes to propound the following questions : 



1 . If a residual clay were to form, in the 

 absence of vegetation, at the present time 

 in the Ozarks, would it be yellow immedi- 

 ately or would it first pass through a stage 

 of red color ? 



2. Did the pre-glacial residual material, 

 in certain districts of the upper Mississippi 

 basin, as, for instance, over the Galena and 

 Niagara limestones of northwestern Illinois, 

 have a yellow stratum over the ordinary red, 

 as in the present subsoil of Stone county, 

 Missouri ? (The remains of the pre-glacial 

 residua yet seen by the writer in north- 

 western Illinois indicate only a red subsoil.) 



3. Is it not possible, indeed probable, 

 that the red clay in southwest Missouri 



represents some ancient period, while the 

 modification of its upper three feet into a 

 yellow clay is peculiarly the result of a 

 more recent period ? 



The writer does not intend to answer 

 these questions, but in conclusion will state 

 one fact, which bears strongly on the last 

 and may be found to be a key to its solution. 

 In some long-past period the streams in 

 Stone county laid down a flood-plain of 

 of gravelly clay and silt of a prevailingly 

 bright red color. Obviously, the material 

 came from the soil and subsoil clay of the 

 surrounding ridges. During a later period 

 the same streams laid down a flood-plain of 

 a light brown and yellow color. Obviously, 

 the material came from practically the same 

 position as during the earlier period. For 

 an explanation of the strong contrast be- 

 tween the two fluvial formations we must 

 look to the surface portion of the residua 

 on the ridges. If we read the evidence 

 aright it indicates that, subsequent to the 

 formation of the first river deposit, a change 

 of climate converted the previously red sur- 

 face portion of the residual clay into a yel- 

 low clay, before the advent of the period dur- 

 ing which the later formation w^as deposited. 



OscAE H. Hershey. 

 Feeepoet, III. 



CUBBENl NOTES ON ANTHROPOLOGY. 

 SOCIAL ORGANIZATION OF THE INCAN GOVERN- 

 MENT. 



Under the title, ' Die sociale Verfassung 

 des Inkareichs' (Dietz, Stuttgart), Dr. 

 Heinrich Cunow, already known by an able 

 treatise on the Australian aborigines, pre- 

 sents an analysis of the government and 

 sociology of the Peruvians before the ad- 

 vent of th€) Spaniards. It is written from 

 a careful comparison of the best early 

 authorities and in the spirit of modern so- 

 ciological science. The subject, therefore, 

 is presented in a widely different light from 

 that offered in Prescott's History. The 



