PETROLEUM 369 



Indian Torritorv' corresponds to that of the salt sand group in 

 Virginia, located in the lower portion of the Potts\'iUe group, 

 resting on the Mississippian limestone, which is in a general 

 way equivalent to the subcarboniferous limestone of south- 

 western Pennsylvania and West Virginia. All the remaining 

 production west of the Mississippi river is secured from strata 

 that are much more recent, reaching from the Permian to the 

 Quaternary-. Tliese newer productive measures consist of 

 much thicker strata — a thickness of 15,000 feet is recorded 

 in localities — and are made up of the recent sedimentary' de- 

 posits. 



The Mississippi river separates the petroleum fields of 

 the United States into two great divisions. The fields east 

 of this line, to an almost universal extent, have developed 

 petroleum with a paraffin base, while the fields to the west 

 have, with a few exceptions, produced petroleum with an 

 asphalt base. Crude petroleum with a paraffin base is gener- 

 ally much lighter and is much more valuable, owing to the 

 greater quantity and superior quaUty of the naphthas and 

 illuminating and lubricating derivatives it yields, as well as 

 the paraffin, which is secured from the hea\'ier distillates 

 after the lighter products have been extracted. 



On the other hand, petroleums with an asphalt base, in 

 most cases, yield only a comparatively insignificant quantity 

 of naphtha and a m^uch smaller proportion of illuminating 

 and lubricating products, which are of inferior quafity, while 

 the remaining distillates are principally valuable for fuel and 

 as asphalts. The asphalt petroleums are also usually much 

 heavier and are more difficult to transport by means of pipe 

 lines, so generally appUed in the fields producing paraffin petro- 

 leum. 



These conditions restrict the market for asphalt petro- 

 leimi, so that in general it is consmned as fuel oil, as distillates 

 for enriching manufactured gas, and as asphalt. There are 

 several exceptions to this generalization, however, as petro- 

 leum, in comparatively small amounts, is found in portions 

 of Kansas, Texas, Indian Territory-, Colorado, and CaHfomia, 

 yielding refined products little inferior to the best grades 

 of paraffin oil. 



Vol. 6-24 



