On the Geological Arrangement of Ancient Strata. 327 



Were it not for the law which permits of the development 

 of these larvae only in the region of which the adult is a true 

 native, the zones of depth would long ago have been con- 

 founded with each other, and the very existence of the zones 

 of depth is the strongest proof of the existence of the law. 

 Our confidence in their fixity, which the knowledge of the 

 fact that mollusca migrate might at first shake, is thus re- 

 stored, and with it our confidence in the inferences applicable 

 to geology which we draw from submarine researches. 



Some of the facts advanced in this communication are new, 

 some of them have been stated before : but all, for which no 

 authority is given, whether new or old, are put forth as the 

 results of personal observation. 



The Geological Arrangement of ancient Strata deduced from 

 the condition of the present Oceanic Beds. By William 

 Rhind, Esq. 



While the conditions of the atmosphere and of the earth's strata have 

 received their full share of the attention of naturalists, comparatively 

 little has been done to investigate the state of the ocean. We still require 

 much information regarding its depth, temperature, currents, and the 

 localization of its plants and animals. 



With the exception of the continents and islands scattered over its 

 surface, the ocean forms a continuous zone of fluid encompassing the 

 globe, and varying in depth from a few hundred feet to perhaps four or 

 five miles. Like the atmosphere, its particles are in continual motion, 

 some portions being rarefied by heat, and others condensed by cold ; 

 while regular currents, produced chiefly by the imequal temperatures of 

 high and low latitudes, continually cause a movement of its waters, and 

 a tendency to an equalization of its general temperature. From the laws 

 which regulate fluids, however, its mean temperature is more uniform 

 and steady than that of the air, and there is loss difference between its 

 polar and equatorial temperature than that which exists in the atmo* 

 sphere. 



Accurate experiments on the temperature of the ocean in different U* 



similar in form to the undeveloped shells above alluded to, and it is yet 

 to be seen whether all Cephalopoda do not commence their existence 

 under a spiral-shelled Pteropodo%is form. 



