468 Royal Society. 



ever was necessary to conduct the operations in the most complete 

 manner ; and, with truly royal munificence, ordered that the whole 

 expense of them should be defrayed by his Treasury. The author 

 never contemplated having the means of making these researches on 

 more than a very limited scale, but he had now the prospect, and it 

 has since been realized, of their being conducted on a very enlarged 

 plan. 



It has been often a subject of regret that experiments of this na- 

 ture, of which the French had set an example half a century ago, 

 had not been followed up. On this subject the author remarks, that 

 the operations are of a nature that scarcely any individual traveller 

 could undertake ; for they require a large body of men, some prac- 

 tised in the art of surveying, and as they can only be carried on con- 

 tinuously after the inundation waters have subsided for some time, 

 and therefore at a season of the year when the heat is excessive, 

 those only inured to the climate could stand the work. 



The place selected for commencing the operations was at the 

 Obelisk of Heliopolis, about six miles below Cairo, the oldest known ; 

 erected, according to Lepsius, 2300 years before Christ. The au- 

 thor having given Hekekyan Bey full and minute directions as to 

 the manner in which the researches were to be carried on, the ob- 

 servations to be made, the plans and reports to be drawn up, and 

 the specimens of soils sunk through to be selected, the operations 

 commenced in June 1851. Sixty men were employed under the 

 direction of Hekekyan Bey, assisted by an officer of Artillery, and 

 some young engineers from the Polytechnic School in Cairo. 



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 10 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 1\ 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. 



