RECORDS OF MEETINGS OF 1908 477 



40 per cent., quartz 5 per cent, and the ores 5 per cent., constituting a quartz- 

 diabase, with normal-diabase and olivine-diabase facies. In the quantita- 

 tive system it is chiefly a camptonose (III, 5, 3, 4), with the acidic dacose 

 (II, 4, 2, 4) facies. The oUvinic ledge is palisadose (IV, V, P, 2), the name 

 here suggested for this hitherto unnamed subrang. 



Slight basic concentration at the contacts, possibly according to Soret's 

 principle, followed by differentiation by gravity during crystallization of 

 the main mass, especially by the settling of olivine and the ores and the 

 rising of the lighter feldspars in the earUer and more hquid stages of the 

 magma, accounts for the facies observed and their present relations. 



Professor Johnson said in abstract: Two theories have been advanced to 

 account for the origin of beach cusps. According to one theory, the cusps 

 result from the accumulation of seaweed along the shore and the breaking 

 of water through the seaweed barrier, removing sand and gravel where the 

 break occurs and moulding the remaining deposits into cuspate forms. 

 According to the second theory, the cusps are formed where intersecting 

 waves reach the shore. There are serious theoretical objections to both 

 these theories and still more serious practical objections. Experiments 

 show that cusps can be formed in the laboratory by parallel waves which 

 are, in turn, parallel to the beach ; and numerous observations seem to show 

 that they are generally so formed in nature. The cause of cusp formation 

 is to be found in the physical properties of fluids descending an inclined 

 plane, as will be shown more fully in a forthcoming paper. 



Professor Reed said in abstract: Nantasket Beach consists of several 

 drumlins tied together and to the mainland by a complex system of tombolos. 

 Some of the drumUns show sea cliffs now abandoned by the waves. From 

 the relations of these cliffs and the more ancient of the beaches, the initial 

 drumlins have been reconstructed. The effect of marine action in cliffing 

 the drumlins and stringing out the eroded material in successive tombolos 

 has been followed through, step by step, until the conditions of to-day have 

 been reached. 



The study shows that Nantasket Beach is not the result of the accidental 

 tying together of a few islands without system, but that it represents one 

 stage in a long series of evolutionary changes which have occurred in orderly 

 sequence and in accordance with deflnite physiographic laws. 



Professor Reed's paper was illustrated and was followed by remarks by 

 Professor Grabau. 



Dr. Berkey said in abstract: The rocks of the Corlandt series are known, 

 through the work of the late Professor J. D. Dana and that of Professor 

 H. S. WiUiams, to occupy an area on the Hudson River just south of 

 Peekskill, N. Y., and to include a very wide range of granitoid medium to 

 basic types of igneous rocks. 



