378 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 13, No. 17 
of Cairo. These tomb chambers, which date from the XIIth dy- 
nasty, about 2500 B. C., were hewn in a stratum of Middle Eocene 
(Mogattam) limestone which here forms the cliffs that border the 
Nile valley on the east.! The adzes, of which many could be found | 
thirty-five years ago on the talus slope, were used for the excavation 
of the chambers according to Seton Karr,? although Petrie’ states 
that they were used ‘for dressing down the walls of the rock cham- 
bers.” Similar, but rougher, adzes were used at the XIIth and . 
XVIIIth dynasty tombs at Qurneh, near the Tombs of the Kings at 
Thebes, and are figured by Petrie.4 One of the adzes that I collected 
was given to the U. 8. National Museum and another to the Metro- 
politan Museum of Art in New York City. 
The adze figured here is 21 cm. long, 8 em. in greatest width, and 
6 cm. in greatest thickness. The proximal end is broken and the 
original length was probably 4 or 5 centimeters more than the pres- 
ent. The adze weighs 1338 grams. 
The material is a dense, very fine-grained, cream-colored, siliceous 
limestone, which is barely scratched by quartz and is therefore much 
harder than the limestone in which the tomb chambers were hewn. 
It is possible that the material came from the vicinity of the tombs, 
but the secondary silica present indicates that it may come from the 
Gebel Ahmar sandstone between Cairo and Suez. 
Study of a thin section under the microscope shows that the rock 
contains much silica, which is apparently of secondary origin, inter- 
stitial between the minute indefinite particles of calcite, with some 
grains of quartz sand. Foraminifera are rather abundant, which 
were determined by Dr. T. W. Vaughan as nummulites and other 
unidentified genera. These fossils are not silicified, but it was 
not ascertained whether they are composed of calcite or aragonite. 
The rock effervesces vigorously with hydrochloric acid, leaving a 
large residue of white silica which retains the form of the rock parti- 
cles. An incomplete chemical analysis gave me the following results: 
SiO, 50.75, AlLO; + Fe.O; 2.63, CaO 25.28, MgO 0.06, CO: (cal- 
culated) 19.92, Sum 98.64. The rock is therefore composed of silica 
and calcium carbonate in about equal parts. Petrie calls the material 
of these Beni Hassan adzes “sandstone,” and Karr speaks of those 
1 For a description of this formation see Renn, F. R. C., The geology of the British 
Empire, 37, London, 1921. 
* Cf. Bupan, E. A. W., The Nile, 645, London, 1907. 
* Perrip, W. M. Furnpers, Tools and weapons, 46, pl. 53, nos. 82-85, London, 1917. 
* Perrin, Qurneh, pl. 9, London, 1909. 
