526 Correspondence—W. B. Wright. 
limestones that are quarried at Gebel Moqattam to the south-east of 
Cairo and elsewhere ; some detailed quarry records are given on the 
authority of the late T. Barron, and a report on the chalky nummulitiec 
limestones used as building stone in Upper Egypt is contributed 
by Mr. H. J. L. Beadnell. There are also notes on sand-lime bricks, 
portland cement, etc. 
CORRESPONDENCE. 
ORIGIN OF THE BRITISH TRIAS. 
Srr,—In the October number of this Magazine Mr. A. R. Horwood 
has given us a summary of the conclusions he has come to as a result 
of his researches into the origin of the British Trias. The paper as 
printed, being only an abstract of a longer paper read at the British 
Association, has no doubt suffered much in clearness as a result of 
condensation. In its present form, however, it is unsatisfactory, being 
composed in part of facts long known and now put forward none too 
clearly and by no means for the first time, and in part of more or less 
new statements requiring substantiation. I feel, and I daresay I voice 
the feelings of other readers too, that I should now like to hear the 
evidence on which some of these last-mentioned statements are based. 
I do not wish for the present to be understood as criticizing the 
conclusions, but merely as asking for a more explicit statement of the 
facts. I will take the points under Mr. Horwood’s own numbers. 
(3) If there is a general absence of delta bedding in the Bunter 
[see (9)], what then is the evidence that it is a delta? Is it its 
dactyloid form (6), and, if so, is this capable of being demonstrated on 
a map ? 
(9) Apart from the fact that beds which should theoretically have 
lain at 40° now lie horizontal, is there any other evidence of tilting 
through an angle of 45° in any part of the Trias? 
(16) I am not very clear as to the author’s meaning here, but 
I presume it is that the signs of wind erosion are confined to one level 
on the syenites and other older rocks. I would now ask how many 
cases of this wind erosion are known and to what extent they can be 
demonstrated to occur only at one horizon in the marls; also whether 
the opportunities for their observation are not very exceptional ? 
(20) What is the evidence that the supposed Bunter river came 
from North-West Scotland? Jam aware that I may be displaying 
great ignorance of the literature of the subject in asking this question, 
but in that case a reference will set me right. 
(21) What are the points of petrographical correspondence between 
the Bunter, Keuper, and modern delta formations? What bearing on 
this question has the immediately following statement that ‘the 
Leicestershire Trias shows signs of chemical action, the Nile delta of 
mechanical ’”’ ? 
W. B. Wricur. 
DvuBLIN. 
