

20 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.38. 



Oasis near the village of Kharga, which is about 300 miles south of 

 Cairo and nearly 100 miles west of the Nile. There are several 

 ranges of small mountains w it hin t he oasis, and in the foothills of one 

 of these, on a conical hill about 20 feet high, the specimens were 

 found Lying loose in the sand. Ill a few places is exposed the solid 

 rock, which is doubtless the Nubian sandstone of Upper Cretaceous 

 age, that plays so important a pari in the scenery of northeastern 

 Africa." 



To convey a better idea of the region, the following description is 

 excerpted from an article by a former member of the Egyptian 

 ( J. ological Survey: 



The Lybian Desert is the easternmost ami most unhospitable portion of the Sahara 

 or Greal Desert of Africa. The region is practically rainless ami the greater portion 

 is quite devoid of vegetal inn, and is uninhabited even by nomad tribes. The extreme 

 barrenness of the desert as a whole, however, is in greal measure counterbalanced by 

 a number of isolated, highly fertile oases, in which then- is a permanent resident 

 population. The chief groups of oases are the Siwan on the mirth, that of Kufra on 

 i In- west, ami the Egyptian, including the four large oases of Baharia, Farafra, Dakhla, 



and Kharga, on il ast. The Egyptian oases occupy extensive depressions cat 



down nearly to sea level through the generally horizontal Cretaceous and Tertiary 

 rocks forming the Lj bian desert plateau. These depressions owe their origin in great 

 measure to the differential effect of subaerial denudation acting on rock masses of 

 varying hardness ami composition. 6 



Description. — The suite contains some eighty-five representative 



specimens, ranging from simple rounded tablets to very involved 

 intergrowths, and varying in size from three-fourths inch (10 mm.) 

 to 21 inches (70 nun.) in diameter. They are composed of about 

 equal percentages of quartz sand ami the mineral barite or heayj 

 spar, and i" color and bister resemble maple sugar. Their surface 

 has a fine-granular appearance because the rounded quartz grains 

 protrude very slightly from the baritic cement. The onl\ crystal 

 face present is Hie basal plane c (001), which, however, is univer- 

 sally developed and controls the habit of every unit and compound. 

 The simplest form, which may be considered the fundamental one, 

 since it enters into t he makeup of every aggregate, is occasionally found 

 in single development, as shown in figs. 1 and I, plate 0. This is a 

 Hal crystal bounded above and below by basal planes and circular 

 in outline with scalloped bolder. To one Looking down upon an 

 edge it has the appearance of being laminated or twinned parallel to 

 the base, and possibl} represents a serrate-edged group produced by 



\ . ( ieike, Tex 1 1 k of Geology, vol. 2, p. I -'!». . 



''II. .1. I.. Beadnell, Flowing wells and Bubsurface water in Kharga Oasis. Geol. 

 Mag., vol. 5, L908, pp. 19-57; L02 L08. For a very entertaining account of this oasis, 

 which combines scientific accuracy with liveliness of portrayal, the reader i> referred 



to a recently published book bj the same author, entitled An Egyptian Oasis; an 

 ace, Mint of the ( iad> nf Kharga in the Lybian Desert. London, 1909. 



