MERIDIANS, MILES, BOTTOM DEPOSITS 421 



Meridians used in some Foreign Charts in 

 Terms of Longitude from Greenwich. 



Amsterdam 4 53' 4" E. 



Cadiz ... 6° 12' 24" W. 



Christiania io° 43' 26" E. 



Ferro .. 18 10' 0" W. 



Lisbon .. 9 7'56"W 



Naples . . 14 14' 43" E. 



Paris . . 2° 20' 15" E. 



Petersburg 30 19' 40" E. 



Nautical and Geographic Miles. 



Nautical mile = 6,080 feet. Geographical mile = 6, 086 feet. 



The nautical mile is one minute of latitude. Since the 

 earth is not truly spherical, the length of a minute of 

 latitude increases from 6,046 feet at the equator to 6,108 

 feet at the poles. For navigational purposes and chart 

 work an average value (6080 feet) is always used. On 

 plans (charts of small area, such as harbours), the "minute 

 of latitude in " the place — that is to say, its true value in 

 the place — is used instead of the nautical mile. 



The geographical mile is one minute of longitude on the 

 equator. 



Abbreviations for Bottom Deposits used in Ad- 

 miralty Charts (Admiralty Chart, X. 11). 



b. blue, 

 blk. black. 



br. brown, 

 brk. broken. 



c. coarse, 

 cl. clay. 



crl. coral. 



d. dark. 



f. fine. 



g. gravel, 

 gn. green. 



grd. ground. 



gy- § re y- 



h. hard, 



m. mud. 



oys. oysters. 



oz. ooze. 



peb. pebbles. 



r. rock, 

 rot. rotten. 



s. sand. 

 sft. soft, 

 sh. shell, 

 spk. speckled, 

 st. stones, 

 stf. stiff, 

 w. white, 

 wd. weed. 



y. yellow, 

 for. Foraminifera. 

 gl. Globigerina. 

 pt. Pteropod. 

 rad. Radiolaria. 



