/j«5 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 



ing at the expense of the sea. It would then appear that the 

 main cause of land movements is pressure from the sea. 



The pressure at great depth in the ocean is, of course, very 

 great, amounting to more than 800 pounds per square inch at 

 five miles. But the differences in water at the surface and on 

 the bottom are not as much as might be supposed. This 

 arises from the very great resistance of water to compres- 

 sion. If the action of gravity were to cease, the surface of 

 the ocean would rise only about 200 feet. The great pressure 

 is manifested in all directions, and sometimes thermometer bulbs 

 are smashed to dust where not sufficienth^ protected in sound- 

 ing. Adequate provision must be made against this enormous 

 pressure, both to prevent what oceanologists call "implosion," 

 as in the case cited, and explosion by outward bursting of wa- 

 ter bottles; for instance, by expansion on reaching the sur- 

 face, through excessive diminution of pressure. 



The water at the bottom of the ocean where it is very deep 

 is extremely cold, even at the troipcs, there being very little 

 difference in temperature at different latitudes. The mud 

 brought up in the dredge is cold enough to be used as ice in 

 cooling bottled beverages. 



The ocean floor is covered with a deposit made up of frag- 

 ments of shells, of vegetable detritus and other fine-grianed ma- 

 terial such as may drop from the rich life-zone of the first 

 600 feet from surface. There are also commonly found minute 

 spherules, of the size of a pin head, say not more than six 

 or eight to a pint of mud, which have centers of dense metallic 

 iron. These are undoubtedly of meteoric origin, apparently 

 contributed from sources outside our own planet. My observa- 

 tions and other records all go to show that there is no such 

 thing as a continuous shower of cosmic dust over the oceans. 



The limits of my time and the lack of illustrative material 

 at hand, as well as the audience before me, forbid more than 

 these broad generalizations here. Much as we have learned, 

 there remain many questions to solve of great interest and 

 of far-reaching importance. Some of these must have great in- 

 fluence upon the future development of geographic and geo- 

 logical science. I thank you for your attention and the in- 

 terest you have shown in this work. 



Dr. Herman L. Fairchild, of the Rochester (N. Y.) University, 



has brought out a new edition of Dana's Manual of Geology, revised 

 in accordance with the new concejjtions as put forth by Professor 

 Chamberlin. Those who accept these principles have faith that their 

 influence upon the science of geology will be as far reaching and as 

 stimulative as were the promulgations of Darwin's and Spencer's tenets 

 in the field of Biologv. 



