190 PHYSICAL GEOLOGY. 



3. ROCK-FORMATION. 



Carpenter, Dr. W. B. On the Conditions which Determine the 

 Presence or Absence of Animal Life on the Deep Sea Bottom. 

 Proc. Oeol. Assoc, vol. iv. no. 3, pp. 176-202. 

 Notes the early researches by Lenz, the vertical distribution of 

 temperature, and the general circulation of the water. In the cold 

 area of the N. Atlantic, Avherethe temperature is under 30° Pahr., the 

 fauna is boreal ; British forms are dwarfed. The general circulation 

 of oceanic water brings all in turn to the surface, where it absorbs 

 oxygen. The Mediterranean has no such general circulation ; its bot- 

 tom water has therefore but little oxygen, and there life is absent. 

 This absence of ]ife is perhaps partly due to muddy sediment. The 

 Red Sea is also cut off from the general circulation ; but the water is 

 clear, and there is probably a deep-sea fauna. The " green sand " of 

 the Agulhas current and elsewhere is probably due to chemical sub- 

 stitution, the organic sarcode of foraminifera having been replaced by 

 silicates, and the calcareous shells dissolved by sea water under great 

 pressure. W. T. 



~ . On a piece of Limestone. Good Words, vol. xvi. pp. 713-720. 



A lecture to the working men of Bristol. 



Cliiircli, Prof. A. H. Eed Chalk and Bed Clay. Cliem, News, 



voL xxxi. pp. 199, 200. 

 Gives the result of analyses of the Eed Chalk of Hunstanton ; shows 

 that it contains (besides the calcium carbonate) silica, ferric oxide, 

 alumina, magnesia, and potash. Compares this composition with that 

 of the red clay of the Atlantic bed, and with the glauconite of the 

 greensand formations; shows that a slight alteration of glauconite 

 would make a product like the red chalk residue, but concludes that 

 further analyses are required. , P. D. 



Dana, Prof. J. D. Corals and Coral Islands. Ed. 2. Pp. xx, 348. 



Plates. 8vo. London. 

 First describes the structure of reefs — the outer and inner reefs, the 

 channels among them, the beach sand-rock, the thickness of reefs, and 

 the formations in the sea outside the barrier reefs. Next, coral 

 islands, their form, structure, and the soundings around them. Then 

 the origin of reefs and islands, of coral sands and reef rocks, and of 

 the shore platform, the effects of winds, the rate of growth of reefs, 

 the cause of the barrier condition and of atolls. Chap. 4 gives the 

 geographical distribution of coral reefs and islands. Chap. 5 the 

 evidences of changes of level in the Pacific, and Chap. 6 the geological 

 conclusions drawn from a comparison of old limestones with the con- 

 ditions above described. W. W. 



