226 Notices of Memoirs— Prof. J. W. Judcl—Nile Delta-Borings. 



1TOTICES O^ 1 HVHIEIIVIIOIEIRS- 



I. — Keport on a Series of Specimens op the Deposits of the 

 Nile Delta, obtained by the Eecent Boring Operations. 

 By J. W. Judd, F.B.S., Pres. Geol. Soc. Proceedings of the 

 Eoyal Society, No. 240, 1886, pp. 213-27. 



THIS paper contains the results of a microscopic analysis of 

 specimens from the borings, which have lately been carried on, 

 under the auspices of the Boyal Society, in three different places in 

 the Nile Delta. That at Kasr-el-Nil, Cairo, was carried to a depth 

 of 45 feet, whilst those at Kafr-ez-Zayat and Tantah, places about 

 half-way between Cairo and the Mediterranean, were 73 and 84 feet 

 deep respectively. In none of these borings was the rocky floor of 

 the Nile valley reached. The beds passed through consisted of an 

 admixture, in varying proportions, of" blown sand and alluvial mud. 

 The sands, when examined under the microscope, are seen to consist 

 of two kinds of grains ; the larger, usually perfectly rounded and 

 polished, are of quartzitic materials evidently derived from granitic 

 rocks, with particles of red and brown jasper, Lydian stone, frag- 

 ments of silicified wood, nearly unaltered felspar grains, hornblende 

 and jade. The smaller sand grains, often subangular and angular, 

 include a greater variety of minerals than the larger, and comprise, 

 in addition to those above mentioned, mica, augite, enstatite (?), 

 tourmaline, sphene, iolite (cordierite), zircon, fluorspar, and mag- 

 netite, all in a nearly unaltered condition. These sand grains have 

 been derived either directly from the breaking up of granitic and 

 metamorphic rocks, or from older sandstones formed of the debris of 

 these rocks. 



The mud is singularly deficient in kaolin, and seems to be com- 

 posed of extremely minute chips and flakes of quartz, felspar, mica, 

 hornblende and other minerals, mingled with some organic particles 

 and frustules of Diatomaceee. In the Tantah boring fragments of 

 tufaceous limestone were also met with. 



The striking feature in the character of these delta deposits is the 

 comparatively unaltered condition of the felspars and other complex 

 silicates in the sands and muds, and the absence of kaolin. Under 

 the usual processes of disintegration of rocks in temperate climates, 

 the felspars and other silicates are reduced by chemical action to 

 soluble silicates of potash, soda, etc., and carried away in solution, 

 whilst the kaolin remains behind. It appears, however, from the 

 nature of these deposits, and from the small amount of soluble solid 

 matter in the water of the Nile, notwithstanding the concentration 

 resulting from extensive evaporation, that chemical action has had 

 but little effect in the drainage area of the Nile, in comparison with 

 the mechanical influences resulting from extreme variations of tem- 

 perature, the action of the winds, and torrential rains. G. J. H. 



