477 
Correspondence — Mr. A. J. Jukcs Browne. 
assign to the Upware rock is, I thinlr, so worded as to convey a 
wrong impression. “ He correlates it witli the lowest portion of the 
Corallian region, on account of its containing Cidaris fiorigemma, a 
reason which would make us assign to it nearly the liighest.” This, 
coupled with the rest. of the paragraph, and their nse of the word 
Corallian, would give rise, I thinlc, to the supposition that I had 
placed the Upware rock below the Coral Rag. On the contrary, I 
take some pains to prove it to be Coral Rag, and the only support 
for this Statement is that, as I was contending against Mr. Seeley’s 
attempt to place the bed in the Kimmeridge series, and as C. flori- 
gemma was then supposed to characterize rather the lower part of 
the Coral Rag, I point out that the affinities of the Upware rock are 
downward rather than upward, so that it cannot even be paralleled 
with the Continental Sequanien. It is true that, according to Messrs. 
Blake and Hudleston, the position of the zone of C. fiorigemma is 
less constant than it was supposed to be ; but in reasoning on that 
point, I used the best information to be obtained at the time, and the 
change does not materially weaken my inain position that the 
Upware limestone is true Coral Rag, as the word was then under- 
stood. 
St. John’s College, Cambridge. T. G. Bonney. 
THE ORIGIN OF CIRQUES. 
Sik, — I n a recent number of the Geological Magazine (p. 273), 
Mr. Bonney has replied to the arguments adduced by Mr. Heiland 
in favour of the glacial origin of cirques (Quart. Journ. Geol. Soc., 
vol. xxxiii. p. 142), and has adduced many cogent reasons in support 
of the explanation he has previously given, viz. “that the cirques 
are mainly produced by the combined erosive action of streamlets.” 
May I be allowed to eite what I conceive to be an illustrative case, 
occurring in a country which I have lately visited, and where it 
would be difficult to discover any traces of ice action, but where the 
erosive power of torrential rains is markedly exhibited ? I refer to 
Upper Egypt, and especially to that district lying between the valley 
of the Nile and the Red Sea. 
The eastern bank of the Nile above Cairo is bordered by a desert 
plain, about three or four miles wide, and Stretching up to the high 
cliffs beyond, which rise into mountains some 600 or 700 feet high, 
and form the ränge known as the Arabian cliain. These cliffs are 
furrowed by numerous deep gorges and valleys opening on to the 
desert plain below, over which is spread out the detritus brought 
down from the hills ; for Egypt is not the rainless country it is 
sometimes represented to be, and in winter-time rain falls occasion- 
ally in quantity sufficient to convert these dry valleys into rushing 
torrents ; thus among the recesses of the bare and barren limestone 
rocks, into which the valleys lead, signs of water-action are every- 
where visible. A cirque in such a land as this could hardly be 
formed by any other agency than that to which Mr. Bonney attributes 
them, and yet a very cirque-like hollow came under my notice while 
exploring one of these ravines. I had ridden some distance along 
