370 Scientific Intelligence . — Hydrography. 



experiment. At 16 fathoms a living creature would have to sustain 

 only about 60 pounds to the square inch, and at 60 fathoms as 

 much as 180 pounds. At 100 fathoms depth the pressure would 

 amount to 205 pounds ; and at 700 fathoms the creature must 

 bear with impunity a quantity equal to 1830 pounds upon the square 

 inch ; while the pressure of 1000 fathoms of superincumbent water 

 on the same area considerably exceeds a ton. — (Rear- Admiral 

 Smyth, K.S.F., on the Mediterranean, p. 193.) 



4. Sea Pressure. — " In proportion to the descent into the sea 

 does the pressure of the superior portion upon the inferior become 

 greater; and as a column of sea water, 11 yards in height, is nearly 

 of the same weight as a column of air of an equal base, extending 

 from the surface of the earth to the limit of the atmosphere, it fol- 

 lows that, at a depth of 1100 yards, the water sustains a pressure 

 of 100 atmospheres. How enormous, then, must this pressure be 

 on beds still lower, if the mean depth of the sea, at a distance from 

 the coasts, extends for several miles, as the laws of gravitation seem 

 to indicate." A question thence arises as to the depth of water 

 necessary to produce the liquefaction of gases. Estimating the 

 height of a column of water equal to the pressure of an atmosphere, 

 in the usual way, at 34 feet, and neglecting the saline contents of 

 the sea, as well as the probable compression of water itself at vast 

 depths, Dr Faraday has shewn (Philosophical Transactions for 1823) 

 the pressure and temperature at which the gaseous substances below 

 enumerated become liquid in his experiments, and it results that 

 those gases could not exist as such below the depths marked in 

 feet on the last column. 



Feet. 

 Sulphurous acid gas liquifies, under 2 atmospheres, at 45° 68 



Cyanogen gas, 3«6 ... 45° 123 



Chlorine gas, ... ». 4 ... 60° 136 



Ammoniacal gas, ... ... 6*5 ... 50° 221 



Sulphuretted hydrogen gas, 17 ... 50° 578 



Carbonic acid gas, ... ... 36 ... 32° 1224 



Muriatic acid gas, ... ••• 40 ... 50° 1360 



Nitrous oxide gas, 50 ... 45° 1700 



— [Rear- Admiral W. H. Smyth, K.S.F.,on the Mediterranean Sea.) 



5. The Colour of the Ocean. — The usual tint of the Mediterranean 

 Sea, when undisturbed by accidental or local causes, is a bright and 

 deep blue ; but in the Adriatic a green tinge is prevalent ; in the 

 Levant basin it borders on purple, while the Euxine often has the 

 dark aspect from which it derives its modern appellation. The clear 

 ultramarine tint is the most general, and has been immemorially 

 nuticed, although the diaphanous translucence of the water almost 

 justifies those who assert that it has no colour at all. Seamen 

 admit of one conclusion in regard to colour, namely, that a green 



