Page:Popular Science Monthly Volume 23.djvu/345

Rh the ancient records of Egypt which lends support to such an hypothesis.

But we are indebted to Dr. Leith Adams for proof that the Nile, between the first and the second cataracts, once stood very much more than twenty-five feet above its present level. From Assouan to Derr, in fact, he observed abundant patches and continuous terraces of alluvium, containing shells of the same kinds of fresh-water mollusks as those which now inhabit the Nile, one hundred to one hundred and twenty feet above the highest level now reached by its waters; and he concludes that "the primeval Nile was a larger and more rapid river than it is now." I am disposed to think that the "primeval" Nile was so, but I question whether these terraces were made by the river in its youth. I see no reason why they should not be affairs of a geological yesterday—say, a mere twenty or thirty thousand years ago.

There can be no reasonable doubt of the correctness of the view first, so far as I am aware, distinctly enunciated by M. Louis Lartet, that the whole of the principal valley of the Nile has been excavated by the river itself. I am disposed, for my own part, to think that the Nile might have done this great work if the mass of its waters had never been much greater than now. And, with respect to the innumerable lateral ravines which debouch into the main valley, I think it-would not be safe to affirm that they could not have been excavated by the rains, even if the meteorological conditions of the country had never been very widely different from what they are now.

But, in some parts of Lower Egypt, and in the peninsula of Sinai, many of the dry wadys exhibit such massive deposits of more or less stratified materials, that it is hardly credible they can have been formed under anything like existing conditions. Indeed, in some localities, very competent observers have considered that there is good evidence of the former existence of glaciers in the valleys of Sinai. And it is well worthy of consideration whether, as Fraas and Lartet have suggested, these deposits were not contemporaneous with the so-called glacial epoch, when the climate of Northern Europe resembled that of Greenland, and when the Mediterranean covered the Sahara and washed the western flanks of the Libyan range.

Under such changed conditions, Egypt must have been one of the wet countries of the world, instead of one of the driest; and, as there need have been no diminution in the bulk of water poured in by the White and Blue Niles, the accumulation of water in the valley of Egypt partly in virtue of its own rainfall, and partly by the