hetiveen Cairo and Suez. 59 



Discussing 0. Fraas's views, he objects to the theory of a gradual 

 passage from the Upper Moqattam into Gebel Ahmar beds, because 

 there is no evidence of limestone and clay in the latter, and further 

 that they have no affinity with the Moqattam beds, but closely 

 resemble the Pliocene sands at the foot of the Moqattam. He 

 found also on examining them that they did not overlie the upper- 

 most beds of the Upper Moqattam, but in different places overlaid 

 different beds at varying levels. This to Dr. Schweinfurth's mind 

 was a proof of the fresh- water character of the deposit. 



After discussing the evidence for and against the idea that the 

 trees in the Petrified Forest have been silicified in situ, he concludes 

 that they have in all probability been transported to where they 

 now lie, and subsequently petrified. The reasons adduced are as 

 follows : — 



1. All the trunks are horizontal ; Figari Bey alone is reported to 

 have found one erect. 



2. No bark has been observed on the trunks, therefore they have 

 not been silicified before being decomposed. 



3. Many trunks appear to have been enclosed in the sand after 

 silicification. 



4. No branches or roots have been found in the district near Cairo. 



5. Stems have been found with only nodes on them. 



This author points out that there is an absence of stratification in 

 the beds, and concludes that petrification must have taken place in 

 a series of basins, because of the difference of level between the 

 places at which the trees are found. 



Professor Sickenberger ^ considered the Gebel Ahmar beds to be 

 of Miocene age. Professor Mayer- Eymar'^ says that after the Lower 

 Tongrian sea had retired and the volcanoes had become extinct, the 

 country became covered by dense forests of trees for the most part 

 of the order Sterculiace^ and the species Nicolia ^gtjptiaca, Unger. 

 Then the subterranean waters, arrested either by the Senonian fold 

 of Ataqa-Abu Eoash or by internal volcanic masses, and heated by 

 the latter, burst out to the right and left below the river of that 

 period, and in the form of warm silicious springs bathed the foot 

 of the trees wherever there was any depression. The trees were thus 

 silicified in sitii. According to this author the age of the Petrified 

 Forest is later than that of the basalt. He is of opinion that Gebel 

 Ahmar is not the product of geyser action, that geysers did not exist, 

 and that the various peaks of quartzite are in each case the product 

 of a strong thermal spring. 



M. Fourtau^ regards Gebel Ahmar and Kreibun as the product 

 of true geysers, and assigns them and the Petrified Forest to the 

 Pliocene period. 



Dr. Blanckenhorn * considers that geysers such as those of 



1 Three lectures on the Geology of Egj^pt, 1891. 



2 Bull, de rinstitut Egyptian, 1893, pp. 393 at seq. 



2 "Etude geol. sur la Gebel Ahmar" (I'lustitut Egj^tien, Decembre, 1891) ; and 

 " L'age des Forets petrifiees des deserts d'Egypte " (Bull. Soc. Khed. Geographie, 

 ser. V, No. 2, 1898). 



* "Das Oligocan": Zeitschr. d. geolog. GeseUs., 1900, pp. 477 and 478. 



