374- Mr Weaver's Vieiso o/Ehrenberg's Observations 



XL. — On the Composition of Chalk Rocks and Chalk Marl 

 by invisible Organic Bodies : from the Observations of Dr. 

 Ehrenberg, By Thomas Weaver, Esq,, F.R.S,, F.G.S., 

 M.R.I.A, Sfc, Sfc, 



[Concluded from p. 315.] 



On the Composition of the Compact Limestone of Upper Egypt 

 and Arabia by the invisible Animalcules of the White Chalk 

 of Europe. 



Both the nummulite limestone of the pyramids of Geza on 

 the left bank of the Nile, and the same kind of rock on the 

 right bank near Cairo, contain numerous microscopic ani- 

 malcules of the chalk, which serve as a cement to the Num- 

 mulites. 1 had often examined microscopically specimens 

 which I had brought from thence, but I did not succeed in 

 separating and rendering visible the different elements with 

 equal cleiirness, until I applied my newly-acquired practice, 

 which was much facilitated by immersing these stones a longer 

 time in water. The same result attended the examination of 

 the other calcareous rock masses of Upper Egypt and Arabia, 

 showing that the animalcules of the chalk occupy in a sur- 

 prising manner a wide extent of country in Libya. 



Nummulite limestone, wherever occurring, has been most 

 usually referred to the tertiary period, although perhaps often 

 belonging to the chalk. In Egypt it possesses no great ex- 

 tent. On the right bank of the Nile it is deposited only in 

 the small hills near Cairo, and on the left bank, as it appears, 

 in a tract extending from Siout to the declivity of the com- 

 pact limestone, which latter constitutes the mass of the rocks 

 that line the course of the Nile in Upper Egypt. It forms 

 the foundation and principal material of the Pyramids. North- 

 ward it is directly bordered by the slimy delta of the Nile, the 

 productive soil of Egypt. Between the Oasis of Jupiter Am- 

 mon and the Mediterranean, is a wide elevated plateau or table- 

 land of rock, among whose numerous organic remains are 

 known tertiary forms. The whole of Upper Egypt, as far as 

 Syene, has a similar character. In 1828, though assured 

 that its limestone rocks were more ancient than the tertiary 

 period, yet, from want of distinct fossils, I was doubtful 

 whether they might not be referred to the Jura formation. 

 On the south, and not far from Syene, this limestone is in- 

 cumbent on sandstone (Quadersandstein ?), and the two repose 

 on granite and the primary rocks connected therewith. I gave 

 these views in 1828 in the geologically coloured map which 

 accompanied the first section of the first volume of my Travels 

 in Egypt, Libya, Nubia, and Dongola. 



It now results, from the microscopic examination which has 



