GEOLOGY AN AID TO COAST SURVEY. 653 



the regular geodetic and hydrographic sur- 

 vey. Here, also, would geological knowl- 

 edge be of great advantage to the explorer. 

 In confirmation of my recommendation I need 

 only remind you of a striking fact in the his- 

 tory of our science. More than thirty years 

 ago, before Dana and Darwin had published 

 their beautiful investigations upon the coral 

 reefs, a pupil of mine, the late Armand Gressly, 

 had traced the structure and mode of growth 

 of coral reefs and atolls in the Jura moun- 

 tains, thus anticipating, by a geological inves- 

 tigation, results afterward obtained by dredg- 

 ing in the ocean. The structure of the reefs 

 of our shores is, therefore, more likely to be 

 fully understood by one who is entirely famil- 

 iar with zoology and geology than by a sur- 

 veyor who has no familiarity with either of 

 these sciences. 



There is another reason why I would urge 

 upon you the application of natural sciences 

 to the work of the survey. The depth of the 

 ocean is a great obstacle to a satisfactory ex- 

 ploration of its bottom. But we know now 

 that nearly all dry land has been sea bottom 

 before it was raised above the level of the 

 water. This is at least the case with all the 

 stratified rocks and aqueous deposits form- 



