238 



Nine pits or excavations were sunk at different distances around 

 the obelisk, each down to the level of the filtration water from the 

 Nile at that season, and as much under the surface of that water as 

 was practicable. The most important of these was one close to the 

 obelisk. The upper surface of the pedestal on which the obelisk 

 rests, was reached at the depth of 5 feet 6 inches below the surface 

 of the ground, Nile mud being accumulated to that height ; the 

 pedestal was 6 feet ] inches in height, and it was found resting on 

 two limestone flags, the upper 16 inches, the lower 15 inches in 

 thickness, and this foundation was laid upon pure quartzose sand. 

 This last was penetrated to the depth of 3 feet 2 inches below the 

 lower layer of limestone. 



The author gives a section and description of each of the nine 

 excavations. But before doing so, he states that he obtained twenty- 

 eight specimens of soils sunk through in different parts of the Nile 

 Valley, eleven of which were carefully analysed at the Royal College 

 of Chemistry, under the superintendence of Dr. Hofmann. A col- 

 lection of specimens, duplicates of which are in the possession of 

 Hekekyan Bey, serve as a standard for the description in his reports 

 of the soils passed through, to avoid the necessity of sending speci- 

 mens of identical alluvia. These samples were carefully compared 

 with the specimens analysed, and were found to resemble them 

 closely in external characters. 



The results of the analyses are given by the author, and the 

 average of eight specimens of Nile mud gives the following com- 

 position in 100 parts : 



Silica 54-585 



Sesquioxide of iron 20'215 



Sesquioxide of alumina 6*418 



Alumina 5'237 



Carbonate of lime 3'717 



Sulphate of lime 0-245 



Lime 1'912 



Magnesia 0'762 



Potassa 0-473 



Soda 0-553 



Organic matter 5*701 



99-818 



