72 SCIENCE AND SOIL 



SOME EASTERN RESIDUAL SOILS 



InTable 12 is given the ultimate chemical composition of residual 

 soils derived from ten different geological formations, and as a 

 rule the results are the average from several samples of the same 

 type of soil. The soils were collected in Maryland, but in most 

 cases the same soil types extend into other states and may be con- 

 sidered as more widely representative of these soil formations. 



The soil analyses 1 were made by Mr. F. P. Veitch of the United 

 States Department of Agriculture, under the direction of Professor 

 Milton Whitney, Chief of the Bureau of Soils, and with the indorse- 

 ment of Doctor H. W. Wiley, Chief Chemist of the Department of 

 Agriculture. 



In all cases the samples analyzed were taken " immediately 

 under the top soil," and thus represent the upper stratum of the 

 subsoil. The results are given in Table 12 on the basis of pounds 

 of the different elements present in 2 million pounds of the soil, 

 corresponding approximately to the amounts per acre in a" 6f -inch 

 stratum. " Volatile " means loss on ignition, and includes organic 

 matter, combined water, probably some sulfur, which may be 

 oxidized from organic matter or from pyrites, and possibly some 

 carbon dioxid (not completely replaceable if derived from magne- 

 sium carbonate). Oxygen may be lost or gained during ignition, 

 depending upon the compounds of iron, sulfur, etc., the amount 

 of organic matter, and the stage to which the ignition is carried. 

 The oxygen is estimated by difference, which really includes errors 

 and all undetermined elements not otherwise reported. 



It should be kept in mind that sandstone does not mean quartz. 

 It means a stone with sand grains cemented together. The sand 

 grains may consist of quartz (silicon dioxid), but more commonly 

 they are grains of silicate minerals, including much aluminum and 

 iron and more or less of the other abundant mineral elements. 

 Residual soils resulting from the disintegration, decomposition, 

 and leaching of the previous geological formations vary with the 

 character of the original rock, and with the loss by leaching. In the 

 case of the limestone formations, it is apparent that the residual 

 soil consists of impurities contained in the original limestone, the 



1 Maryland Agric. Expt. Station Bulletin 70. 



