DEMONSTRATION MATERIAL IN GEOLOGY 79 



which Atlantic City is built, and lagoons back of the islands; let the 

 lagoons then be filled with sediment and organic matter; let the reel, 

 later, show the erosion and final disappearance of the barrier islands and 

 the marsh lands back of them. Let the scene close with a slight sub- 

 mergence and the production of a coast like that of Virginia and North 

 Carolina. 



(2) Most students of elementary geology have difficulty in recognizing 

 regions in youth, maturity, and old age. A moving picture showing a 

 region passing through these stages could be shown and would be most 

 helpful. 



(3) A moving picture of the. geological history of the Appalachian 

 Mountains would first show the deposition of sediment in the geosyn- 

 cline; then the earth's crust slowly yielding to pressure and the folding 

 of the sediments; a slow emergence from the sea; a halting, with, per- 

 haps, peneplanation ; after erosion a further submergence and deposition ; 

 then elevation, peneplanation, and the warping of the peneplain ; the 

 intrenching of the streams and the final reduction of a part of the region 

 to a second peneplain. In other words, it should reproduce as nearly as 

 possible the history of mountains of the Appalachian type. 



(4) Diagrams showing the flooding of the Connecticut Valley as New 

 England was lowered during the Champlain epoch, the filling of the 

 valley with sediment, the raising of the land, and the formation of rock- 

 defended and other terraces would be welcome. 



(5) The formation of faults, with fault-line topography, and the grad- 

 ual obliteration of the fault-scarps by the agents of weather and erosion 

 could be shown on the screen. 



(G) A motion picture of an igneous intrusion working its way toward 

 the surface by stoping and melting; the formation of a volcano; the 

 extinction of the volcano and the birth of others from higher points of 

 the injected body would be extremely valuable. 



(7) A motion picture of the geologic history of the Hudson Kiver 

 Mould be of interest to a great many people, as one-twelfth of the popula- 

 tion of the United States is said to be within a radius of 25 miles of the 

 Statue of Liberty. 



(S) Animated diagrams of mountain glaciers, particularly showing 

 erosion and deposition and the carving of mountain scenery, would be 

 largely used. 



(9) Many other subjects which lend themselves to this treatment will 

 come to your minds, such as the origin and accumulation of oil and gas 

 and its exhaustion; the formation of coral islands by both Daly's and 



