189 



3. ROCK-FORMATION. 



Boulger, Prof. G. S. Rocks of Animal Origin. Proc. W. Lond. Sci. 

 Assoc, vol. i. pt. iii, pp. 103-109. 



The Laurentian graphite and ironstone are probably due to vegetal 

 organisms. All limestones are of organic origin. The formation from 

 organic sources of chalk, greensand, red clay, and " coprolite " is 

 referred to. W. H. D. 



Duncan, Prof. P. M. Limestone Makers. Nature, vol. xiv. pp. 9, 

 10. 



The form described by Mr. Munro (see below) as contributing largely 

 towards the formation of coral-sand is the genus Corallina, a very com- 

 mon limestone-maker at the Bermudas. F. D. 



Hardman, E. T. The Deep-sea Manganiferous Muds. Nature, 

 vol. XV. pp. 57, 58. 



Suggests that the GIohi^erina-Bhelh may have contained carbonate 

 of manganese derived from sea water, which carbonate would be dis- 

 solved as the shell passed through water charged with carbonic acid and 

 oxygen, and the manganese would be deposited as a peroxide. C. E. D. 



Jukes-Browne, A. J. The Origin of the Greensand. Sci. Goss. No. 

 134, pp. 30, 31, No. 140, pp. 170, 171. 



Insists, in opposition to a paper by Mr. Stewart (see Geological 

 Record for 1876, p. 192), that "some greensands do mainly consist of 

 foraminiferal casts," giving as an example the Cambridge bed, which 

 contains glauconitic casts in abundance. The second part is purely 

 controversial. W. W. 



Malet, H. P. Flints in Chalk. Latid and Water, Oct. 7, p. 246. 

 Gives suggestions as to the mode of formation of the layers and 

 nodules of flint in the chalk. 



Monckman, J. The Staining of Eocks beneath the Magnesian Lime- 

 stone. Giol. Mag. dec. ii. vol. iii. pp. 476, 477. 



Endeavouring to account for some of the Carboniferous rocks having 

 been stained through being overlain by Magnesian Limestone, an 

 experiment was made in which water containing carbonic acid and 

 limestone-powder was dropped on grit and stained it dark red, though 

 no iron could be detected in the liquid. W. H. D. 



Munro, John. On the Formation of Coral Sand. Nature, vol. xiii. 



pp. 510, 511. 

 At Santa Cruz, W. Indies, the coral-limestone is made up of coral- 

 blocks, consolidated coral sand and mud, shells, &c. The mud may be 



