OCEANOGRAPHY. 411 



the Gulf Stream. The accumulation of the resulting debris of rocks 

 forms the banks of Newfoundland. • 



These ice fields are of particular interest because of the fear they 

 inspire, because of the shoals formed by their melting - , and particularly 

 because the chilling occasioned by their contact with an atmosphere 

 warmer and more saturated with moisture, gives rise to heavy fogs. 

 Hundreds of disasters would be avoided, enormous economy in the 

 transportation of merchandise would be effected if we could succeed 

 in understanding and foreseeing these phenomena. The admirable 

 pilot charts published every month by the Hydrographic Bureau at 

 Washington seek to solve the problem empirically, noting to what 

 latitude the ice fields descend each year, observing their number, and 

 establishing the probabilities concerning them according to the average 

 of numerous observations. Fogs due to analogous causes — that is to 

 say, to marine currents — are frequent in the northern or even the tem- 

 perate region, on the North Sea, the English Channel, and on the 

 Atlantic coasts of England and France. Everywhere they are the 

 terror of sailors; ships move in them bewildered, advancing at the risk 

 of running ashore or colliding with another vessel, while if they remain 

 stationary they are in danger of being themselves struck, and in any 

 case they lose time, that precious commodity whose price rises higher 

 every day. The ability to foresee their presence, or if overtaken by 

 them to find the course and follow it with certainty, would be the imme- 

 diate consequence of the perfecting of oceanography. 



Some attempts at this have been crowned with success. The position 

 of a ship in the ocean is usually determined by the aid of astronomical 

 coordinates. According to the observed position of a heavenly body, 

 star or sun, the observer calculates his own position on the surface of 

 the waves. Knowing where he is aud where he is going, nothing is 

 easier for him than to follow his course. But the indispensable con- 

 dition is to see the star; this the fog renders impossible. This impos- 

 sibility is the cause of most shipwrecks. However, the position can be 

 otherwise determined. If we have a so-called bathymetric chart, 

 plainly indicating by means of contour lines the depth of the water at 

 each point, and another chart drawn up after a series of soundings and 

 of preliminary analyses showing in the same part of the sea the changing 

 nature of the bottom, here sand and there mud of one kind or another 

 and there rocks, by a single cast of the lead a vessel lost in the midst of 

 the ocean can determine her position. The depth of the sounding will 

 confine the observation to the area for which the bathymetric chart 

 gives this depth. If, moreover, care has been taken to fit the sounding 

 lead with some means by which a sample of the bottom may be brought 

 up, the area covered by this kind of bottom may be looked up on the 

 lithologie chart, and, combining this information with the preceding, 

 one will be able to ascertain his position almost exactly. Excellent 



