Correspondence — " The Delta of the Nile.'^ 479 



way journey to London, Canon Xingsley gives a brief notice of the 

 succeeding rocks up to the Bagshot Sand. Chapter 4 is on "The 

 Coal in the Fire," and explains the origin of coal. Chapter 5, on 

 " The Lime in the Mortar," treats of Limestones and Coral-reefs. 

 And Chapter 6, on " The Slates on the Eoof," deals with the older 

 rocks and volcanoes ; and here we may state that the notion of 

 mountain chains being due mainly to contraction, needs correction 

 on the part of the author, who remarks that "the loftiest mountain 

 chains are nothing but tiny wrinkles." The new edition of Jukes's 

 Manual will give the latest information on this subject. Otherwise 

 we may congratulate the author on the easy and interesting, and yet 

 accurate manner in which he has illustrated " Town Geology." 



"A CRY FROM THE LAJSTD OF EGYPT." 



Sib, — While the Source of the Nile has been honoured by the 

 concentrated attention of Geographers, it has been my own fate to 

 suffer the cruellest mortifications — it pains me to have to add — " in 

 the house of my friend," the Geologists. 



The controversy on the origin of the Wealden, between the 

 advocates of the Lake- and Delta-theory respectively, has been 

 prolonged in its duration, and often doubtful in its results ; but 

 some have supposed this may be only a necessary consequence of 

 the slowness of the methods of inductive research. Fortunately, 

 however, the author of a paper in the last number of the Quarterly 

 Journal of the Geological Society has discovered a summary way of 

 settling this long- vexed question ; discarding the old and tedious 

 methods of inquiry, he has succeeded, by the application of a few 

 very simple crucial tests, in so triumphantly establishing the Lake- 

 theory, as actually to reduce it to an axiom, and to employ it as the 

 basis of a number of highly curious speculations. 



It is impossible to exaggerate the striking novelty of the views of 

 Mr. Meyer on the subject of estuarine deposits. I quote the para- 

 graph in which he enumerates the crucial characters which, found 

 in the Wealden, demonstrate the impossibility of that formation 

 having originated in a delta. 



" The exceedingly quiet deposition of much of the sedimentary 

 strata, the almost total absence of shingle, the prevalence, both 

 numerically and specifically, of such species of mollusca as abound 

 in quiet waters, the comparative absence throughout the greater 

 portion of the series of broken shells such as always abound in 

 tidal rivers, and, I believe I may say also, the total absence of drift 

 wood pei'forated by mollusca in either the Purbeck or Wealden 

 strata, all seem to me to point to the same conclusion — namely, to 

 the accumulation of such strata beneath the waters of a wide but 

 shallow lake, etc." — Quart. Journ. Geol. Sac, vol. xxviii., p. 243. 



In order to appreciate the high originality of these ideas, it is 

 only necessary to reflect on the opinions which have hitherto pre- 

 vailed on the subject. Earlier writers, whether travellers, physical 



