432 Miscellaneous. 



As I have said in tlie last chapter of " Eain and Rivers," amid the 

 apparently hopeless irregularity in all Deltas, there is this one 

 general tendency, that the entire overflow is from a central channel or 

 channels, and the entire escape of the overflow to the sea is by the 

 two side channels. These two sides and the sea-side form the 

 triangle, or Greek Delta, from which these formations receive their 

 name. Besides the earlier deposit of the heaviest materials, this 

 side-escape of the flood-water causes the slope downward from 

 centre to side of Delta deposits. Inland deposits frequently slope 

 the contrary way, from side to centre. For besides that the flood- 

 water has no side-escape, but returns to the river over the same 

 surface which it has traversed, the erosion of the hill-sides and of 

 old terraces tends to heap from the side to the centre. Sometimes, 

 however, channels are ctit by the return water. In this case, a slope 

 from centre to side may be observed even in inland alluviums. 



The Eev. Mr. Bonney, in your May number, applies my theory for 

 the formation of inland terraces (Geol. Mag., May, 1867) to the 

 formation of marine terraces, to which it is wholly Miapplicable. I 

 agree with that close observer and accurate thinker, Professor 

 Kjerulf, in thinking that inland and marine terraces result from 

 causes totally distinct, 



Bkookwood Paek., Alresford, Geobge Geeenwood, Colonel. 



Zrd Auffust, 1871. 



nvcisoEXjiLJLnsriHiOTJS. 



We understand that there will shortly be published a Geological Atlas of England, 

 by Mr. ^Y. Stephen Mitchell, M.A., LL.B., F.L.S., F.G.S. The Atlas will contain the 

 following Maps : — 1. Cambrian (of Survey) ; Lower Cambrian (of Sedgwick). 2. Lower 

 Silurian (of Survey) ; Middle and Upper Cambrian (of Sedgwick). 3. Upper Silurian 

 (of Survey) ; Silurian (of Sedgwick). 4. Old Red Sandstone ; Devonian. 5. Carbon- 

 iferous Limestone ; Yoredale Beds. 6. Millstone Grit ; Coal Measures. 7. Permian 

 (of Survey) ; Pontefract Group (of Sedgwick). 8. New Red Sandstone ; Rhfetic 

 (Penarth). 9. Lias. 10. Lower Oolite. 11. Middle Oolite. 12. Upper Oolite. 

 13. "Wealden; Neocomian. 14. Gault; Upper Green Sand; Chalk and Chalk Marl. 

 15. Eocene. 16. Crag. 17. Alluvium. 18. Bone Caves. 19. Metamorphic (?) 

 20. Igneous. — The Maps will be printed in colours, each Map exhibiting only the 

 range of one formation, and the names of places on the formation. In some few 

 cases, where it is requisite, as a clue to the locality, to introduce the names of places 

 near, but not on the formation, these will be printed in a different type. The Maps 

 (llf in. by 9iin.) are based on a photographic reduction of the last edition of the 

 Greenough Map, which is published under the direction of a Committee appointed by 

 the Geological Society. In all cases where, through researches more recent than this 

 last edition, any changes have been adopted in the grouping of the beds, this Atlas 

 conforms with the latest alterations. The revision of the proofs of particular Maps 

 has been kindly promised by W. Boyd Dawkins, Esq., M. A., F.R.S., W. Whitaker, 

 Esq., B.A., F.G.S., H. Bauerman, Esq., F.G.S., J. W. Judd, Esq., F.G.S., Charles 

 Moore, Esq., F.G.S., "W. T. Aveline, Esq., F.G.S., and others. — Letter-press will 

 accompany each Map, giving in a tabulated form the subdivisions of the formations, 

 the origin of the names of the groups of beds, their lithological characters, thickness, 

 range, etc., with a historical notice of the various classifications that have been at 

 different times employed. —The Lists of Fossils will be arranged on a new plan, 

 showing in a tabulated form for each formation the genera that first appear, those 

 that last appear, and those that are numerically abundant in that formation. Separate 

 tables give the characteristic species. These lists are prepared expressly for this work 

 by R. Etheridge, Esq., F.R.S., F.G.S., etc., PalEeontologist to Her Majesty's Geo- 

 logical Survey of Great Britain. 



