124 
MR. HORNER ON THE ALLUVIAL LAND OF EGYPT. 
Cairo was afterwards added, with the necessary instruments, to make plans and sec- 
tions and to take the levels of the ground. Twenty Bedouin labourers were also 
engaged. 
Eight pits or excavations were sunk around the obelisk at different distances, in 
the situations indicated in the annexed ground plan, and they were carried down to 
the lowest level of the waters of infiltration in the Heliopolis district on the 16th of 
July. 
Fig. 3. 
Relative situations of the pits at Heliopolis. 
[The figures indieate the distances in yards between the pits.] 
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Before beginning to describe the several excavations, it will make the descriptions 
of them more intelligible and will save repetitions, if I give an account of the nature 
of the soils sunk through. 
As it was to be expected that, on the same level, and within a space of moderate 
extent, there would be an identity of composition, I requested Hekekyan Bey to send 
me specimens of all the varieties of soil he met with in sinking the pits, he himself 
keeping corresponding specimens ; thus establishing a standard to refer to in his 
reports, and saving the necessity of sending specimens of identical alluvia. My request 
however was not made until he was carrying on similar researches in the district of 
Memphis, and they were selected from his excavations there ; but they have equally 
served as a standard of comparison for the soils sunk through at Heliopolis, samples 
of which were in my possession when I made the request. 
All the Nile mud, properly so called, has at one time or other been suspended in 
its water. I was therefore desirous that an experiment should be made to ascertain 
the quantity of solid matter held in suspension in the water, at a given place near 
Cairo. Having communicated my wish to Mr. Murray, he prevailed upon Dr. Ab- 
bott, a physician long resident at Cairo, to undertake the inquiry. I then described 
the process and apparatus by which I had in the year 1832 ascertained the amount 
