xiv CONTENTS. 



PAGE 



4. Ships repaired without leaving the water, and even while 



under sail ........ 259 



5. Sensations of the diver — Depth to which it is possible to 



descend 2GI 



6. Extreme difficulty of working below water — Submarine 



foundations — Stone worked when in position . . 266 



7. Diving-bells — Stationary com[)ressed-air apparatus . . 270 



8. Payerne's submarine hydrostat ..... 274 

 D. Villeroy's submarine boat ...... 278 



10. Employment of torpedoes in clearing channels and the 



entrances to ports 280 



1 1 . English mines beneath the ocean ..... 284 



CHANGES IN PROGRESS AT THE BOTTOMS OK SEAS.— 

 THEIR UNIVERSALITY. 



1. Extent of the movements of the terrestrial crust — Nature 



incessantly at work — The gradual cooling of the earth a 

 cause of its present form, owing to the crumpling and 

 breaking of its crust 286 



2. The shore — Its apparent fixity — Traces of the presence of 



the ocean almost universal ..... 295 



3. Progressive enlargement of the Straits of Gibraltar during 



the historic period — Columns of the ancient Temple of 

 Hercules submerged — Descriptions left by Avienus, 

 Pliny, and Pomponius — Mellaria, Carteia, and Belon 

 submerged — Other examples of cities and islands covered 

 by the waters, and of mountains violently separated 

 from continents ....... 298 



4. The quantity of water which covers the earth is sensibly 



constant — An elevation in one point is balanced by a 

 corresponding subsidence in another — Aristotle's opinion 

 about the Greek traditions of the Deluge — The earth will 

 become dryer and colder . ..... 304 



SUDDEN MOVEMENTS OF THE SUBMARINE SOIL. 



I. Earthquakes modify the bed of the ocean— Submarine 



A'olcnnoes ........ 308 



