182 PHYSICAL GEOLOGY. 



3. ROCK-FORMATION. 



DtTRHAM, William. Suspension of Clay in Water. Chem. News, 

 vol. XXX. no. 767, p. 57. Abstract of a paper read to Eoy. Phys. 

 Soc. Edin. 



The power of water to hold clay in suspension is gradually destroyed 

 by the addition of an acid or of common salt, while it is increased by 

 the addition of small quantities of the alkalies or their carbonates and 

 by lime. 



[A letter signed " T. E. 0." (no. 769, p. 97) calls attention to 

 Dr. Sterry Hunt's observations on this subject, which are similar to 

 those of Mr. Durham.] F. W. E. 



Hunt, Dr. T. S. The Origin of Metalliferous Deposits. Trans. 

 Amer. Inst. Min. Eng. vol. i. pp. 413-426. 



Describes the various processes that have resulted in the formation 

 of metalliferous deposits, which the author believes is now going on 

 by means of the same agencies as during past times. W. W. 



KiNAHAK, G. H. Peat Bogs. Quart. Journ. Sci. no. xliii. p. 294. 



On the formation of peat-bogs and its bearing upon the origin of 

 coal. The normal lowland or " red bogs " of the central plain of Ire- 

 land are generally supported by an underclay penetrated by roots of 

 oak and yew. Above the " corkers " or roots of the oak comes a 

 variable thickness of peat, and above that the remains of a pine forest, 

 with the " corkers " in horizontal layers. Eelics of human workman- 

 ship are found beneath the peat. Taking the case of Castleconnel bog, 

 Co. Limerick, the author estimates that at least 5000 years must have 

 elapsed since the oak-forest began to grow there. A. H. G. 



MiJLLER, Alexander. Die EoUsteinrucken. [Pebble-ridges.] Pogg. 



Ann. Bd. clii. pp. 482-484. 

 Suggests that ridges of pebbles may have been accumulated by sub- 

 marine action when the shore was fringed with ice. 



EoBEETSON, David. Note on the Precipitation of Clay in Eresh and 



Salt water. Trans. Geol. Soc. Glasgow, vol. iv. part 3, pp. 257- 



259. 



An account of some experiments which show that salt water has 



much greater power of precipitating clay than fresh water has, the 



difference being marked even between slightly brackish water and pure 



water. G. A. L. 



EopER, E. C. S. What is Chalk ? Papers Eastbourne Nat. Hist. 

 Soc. 1873-74, pp. 7-9. 



An account of the facts which have enabled scientific men to deter- 

 mine the origin of our chalk, leading to the conclusion that " the 

 greater part of the mass is made up of Eoraminifera, with coccoliths 

 and coccospheres." W. W. 



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