190 PHYSICAL GEOLOGY. 



produced by the trituration of coral-skeletons ; but the coarse-grained 

 calcareous sand consists of fragments of the calcareous skeleton of a 

 sea-weed which grows plentifully on the reefs. The sand on the beach 

 was chiefly made up of scales of the sea- weed, more or less worn. (See 

 Duncan, above.) P. D. 



Murray, J. On the Distribution of Yolcanic Dehris over the Floor 

 of the Ocean, — its character, source, and some of the Products of 

 its Disintegration and Decomposition. Proc. R. Sgc. Edin. vol. ix. 

 no. 96, pp. 247-261. 

 Describes the instruments in use for obtaining information on the 

 deposits, and enumerates the various kinds of volcanic dehris found, 

 and some of the products of their decomposition, concluding that 

 clayey deposits far from land are chiefly derived from the felspars of 

 fragmental volcanic rocks. Gives an account of the occurrence of per- 

 oxide of manganese, native iron, and cosmic dust. H. A. N. 



. Preliminary Eeports to Prof. "Wy ville Thomson on Work done 



on board H.M.S. 'Challenger.' Proc. B. Soc, vol. xxiv. p. 471, 



pi. 20. 

 A detailed list of soundings made is classed under the following 

 heads : — Shore Deposits (blue and green muds, near the shores of 

 most of the great continents and islands ; grey muds and sands, near 

 oceanic islands of volcanic origin ; red mud, E. coast of S. America ; 

 coral mud, near coral reefs). Globigerina-ooze, an oceanic deposit not 

 met with S. of 50° S. lat. Padiolarian ooze, an oceanic deposit only 

 in the W. and Mid Pacific. Diatomaceous ooze, an oceanic deposit met 

 with only S. of 50° S. lat. lied and grey clays, the most abundant 

 oceanic deposits. Remarks on the origin of deep-sea clays. 11. E., Jun. 



Pankhurst, E. A. Some of the Problems connected with the De- 

 position and Crystallization of Silica. 23rc? Ann. Bep. Brighton 

 Nat. Hist. Sac. pp. 142-158. 

 Refers to the presence of soluble silicates in mineral springs and sea- 

 water, the manganese nodules of the Pacific, the Triassic Beekites, 

 agates, opal, flint, and the general chemistry of hydrous silica. W. H. D. 



Potter, C. The So-called Porest Beds. 2Snl Ann. Bep. Brighton 

 Nat. Hist. Soc. pp. 10-12. 



Argues, from observations in Cheshire, against the forest-beds being 

 in place. There is but 1 butt to 10 trunks ; and the expansion in 

 growth of roots would have destroyed the lamination of the silt in which 

 they are imbedded. W. H. D. 



Ramsay, William. On the Influence of various Substances in Ac- 

 celerating the Precipitation of Clay suspended in Water. Quart. 

 Journ. Geol. fSoc. vol. xxxii. pp. 129-132. With note by Prof. A. 

 C. Ramsay. 



Those salts in solution which absorb most heat in dissolving precipi- 



