60 PROCEEDINGS OF THE PHILADELPHIA MEETING 



in many areas by differential crustal movement concomitant witti increase in 

 volume of oceanic water through deglaciatlou. 



5. The width of a submerged platform bordering a laud area is indicative 

 not of the amount of submergence, but of the stage attained by planation 

 processes. Other conditions being similar, the longer the period of activity o^ 

 such processes, the wider will be the platform. 



6. The principal value of the coral-reef investigation to geology consists not 

 so much in what has been found out aboui corals as in the study of a complex 

 of geologic phenomena, among which coral reefs are only a conspicuous in- 

 cident. 



Read in abstract from manuscript. 



Discussion 



Dr. Wayland T. Vaugiian, in reply to tlie question of Doctor Pilsbry as to 

 tiie signihcance of the Funa Futi Ijoiiug, stated tliat, because of inadequate 

 Ivuowledge of the stratigraphic distribution of the organisms encountered in 

 the bore hole, the geologic age of the formation penetrated could not now be 

 determined. He also stated that there were certain features of Funa Futi 

 which indicated that there had probably been oscillations of sealevel. 



Prof. A. W. Geabau : Louis Agassiz in one of his early letters speaks of the 

 imix)rtance of coralline algae in the formation of reefs at Florida. He con- 

 sidered the nullipores more important than the corals in this connection. 



Doctor Vaughan, in reply to Professor Grabau's remarks concerning the 

 constructional role of coralline algae along the Florida reef, stated that the 

 coralline alga*, in his opinion, were subordinate in importance to corals, al- 

 though they contribute relatively large amounts of calcium carbonate to the 

 sea-bottom along the reef tract. In the shoal waters of southern Florida and 

 the Bahamas bacteria are the most important agency whereby calcium car- 

 bonate is taken from the sea-water. The others, rated according to importance, 

 are probably (1) foraminifera, (2) mollusks, (3) corals, and (4) coralline 

 algae. 



CAUSES PRODUCING SCRATCHED, IMPRESSED, FRACTURED, AND RECEMENTED 

 PEBBLES IN ANCIENT CONGLOMERATES 



BY JOHN M. CLABKE 



(Abstract) 



The Devonian conglomerate lying beneath the fish-beds of Migonasha, Prov- 

 ince of Quebec, is a characteristic "Nagelfluh" filled with scratched, fractured, 

 and deeply impressed pebbles. Specimens exhibited indicate that the explana- 

 tion of the phenomena of impression by solution, as suggested by Sorby, Heim, 

 Kayser, and others, is inadequate, and that the effects described are in large 

 part actually due to forcible contact resulting from internal friction. Some 

 of the pebbles show unqualified evidence of glacial scratching, and the entire 

 mass is regarded as an outwash from glacial moraine. 



Presented in full from manuscript. 



