This map of [he Mediterranean shows most of 

 the sites of the submerged cities and ancient 

 wrecl<s mentioned in this chapter. Sunl<en 

 cities for which there is evidence, but which 

 have not yet been expiored, are a/so plotted. 



ing the survey in relation to the coast, and a base Une must be set 

 up on land. From this line key points such as rocks, islands, and 

 important buildings are fixed by theodolite, or alidade and plane 

 table. Submerged buildings can be marked with buoys, and these, 

 too, are fixed from the shore. For more detailed work divers can 

 then operate with plastic tapes and rules to measure city block 

 dimensions, wall thicknesses, street widths, and so on, which reveal 

 the detailed plan of the submerged city. 



Aerial and underwater photographs both are a great help where 

 the water is clear enough. While aerial photographs reveal the 

 general plan of a submerged city, underwater photographs provide 

 the diver with a permanent record of what he has found, and 



138 



