239 



In order to ascertain the amount of solid matter held in suspension 

 in the water of the Nile near Cairo, the author described to Dr. Ab- 

 bott, a resident in that city, the method he had followed in 1832 to 

 determine the amount of solid matter suspended in the water of the 

 Rhine at Bonn, and requested him to undertake the experiment on 

 the same plan, which he did, and the result gave 110' 6 grains in an 

 imperial gallon. The residuum sent was analysed at the Royal Col- 

 lege of Chemistry, and yielded very nearly the same result as to com- 

 position as the above average analysis of the Nile sediment. 



On examining the descriptions of the soils sunk through in the 

 nine excavations at Heliopolis, it appears that they consist of two 

 principal kinds, viz. earths and sands. The earths vary in colour, but 

 are so nearly allied, passing by such insensible shades into each 

 other, and having so great a resemblance to the modern Nile sedi- 

 ment, that they may all be classed as Nile mud. The sands are 

 almost entirely pure quartz, similar to those of the adjoining deserts. 



In the same horizontal plane, even in this limited space of half a 

 square mile, there is a very considerable difference in the nature of 

 the soil, and in none of the excavations was there an instance of 

 lamination in the deposit. 



When it is considered how small is the amount of sediment left 

 annually by the inundations in any one place, it is very difficult to 

 conceive, in the author's opinion, how there should be in any one 

 spot so great a thickness as 1 2|- feet of one kind of sediment, as is 

 the case in one of the excavations, without any lamination or other 

 sign of successive deposition, and still more inconceivable that in 

 pits within a very short distance of each other different kinds of soil 

 should be found at the same levels. Other causes than the tran- 

 quil deposit from inundation water must have been at work in the 

 formation of this portion of the alluvial land. The layers of sand 

 were most likely blown across the valley from the desert. 



The author deems it advisable to abstain from general remarks, 

 and from all inferences as to the secular increase of the alluvial de- 

 posits, until he has had an opportunity of laying before the Society 

 an account of the far more extensive researches made in the district 

 of Memphis in 1852, and during the last year in a series of pits 

 sunk in a line across the valley of the Nile, extending from the 

 Libyan to the Arabian Chain, in the parallel of Heliopolis. 



