RECENT ADVANCES IN SCIENCE 35 



ceans, alcyonarians, and one group of brachiopods. These 

 chemical variations are of great significance in the study of 

 coral reefs. In certain groups of organisms, especially crinoids 

 and alcyonarians, it is shown that specimens from warm waters 

 are richer in magnesia than those from cold waters. 



The work of Johnston and Williamson on inorganic agencies 

 in the deposition of calcium carbonate is a severely technical 

 piece of chemical work which has, however, a considerable 

 geological bearing. They call attention to the importance of 

 the factor of relative degree of concentration with respect to 

 calcium carbonate in the ocean, since the chance of a per- 

 manent deposit is the greater the more nearly saturated the 

 surrounding water is. The conditions of solubility have now 

 been accurately determined by experiment. The facts thus 

 obtained, together with the known calcium carbonate content 

 of oceanic water, especially the warmer surface layers, make 

 it clear that a greater importance than heretofore must be 

 assigned to inorganic reposition of this material, although, of 

 course, organic agencies must still be given first place. 



The important paper by Andree on stratification treats of 

 no fewer than eleven different kinds of bedding, all included 

 under the two great groups of normal or concordant stratifica- 

 tion (Parallelschichtung), and discordant or diagonal stratifi- 

 cation (Schragschichtung). In the majority of cases bedding 

 is believed to be caused by variations in lithogenetic con- 

 ditions, although gaps in sedimentation are believed to be also 

 an important contributory cause. There is a full discussion 

 of the phenomenon of rhythmic sedimentation, and the need 

 for exact experimental investigation (such as that recently 

 carried out by G. K. Gilbert) indicated. 



Haberle's paper deals with the peculiar spongy or honey- 

 comb weathering of sandstones, of which, perhaps, the best 

 British examples are found in Arran. Wind may play a 

 dominant part in the production of these forms in arid regions, 

 but they are not confined to or characteristic of these regions. 

 The author believes the general cause of the phenomenon to 

 be the solvent action of water circulating through the rock 

 along well-defined paths, loosening the grains by solution of 

 the cement, and thus exposing them more completely to erosive 

 agencies where these paths reach the surfaces of the rock. 



In his short paper on the rhythmic deposition of flint Prof. 



