72 DIVERSIONS OF A NATURALIST 



waters above and to the side. Their inhabitants are 

 different from those of the warmer water. They are due 

 to the melting of the polar ice, the cold water so formed 

 sinking at once owing to its greater density below the 

 warmer water of the surface currents. These deep 

 currents originate in both the Arctic and Antarctic regions, 

 and the determination of their force and direction, as 

 well as of those of other ocean currents, both deep and 

 superficial, such as the warm " Gulf Stream," which 

 starts from the Gulf of Mexico, and the great equatorial 

 currents, is a matter of constant study and observation, 

 in which surveying ships and skilled observers have been 

 employed. 



Amber has not only been valued for its beauty of 

 colour — yellow, flame-colour, and even deep red and 

 sometimes blue — for its transparency, its lightness, and 

 the ease with which it can be carved, but also on account 

 of certain magical properties attributed to it. Pliny, the 

 great Roman naturalist of the first century A.D., states 

 that a necklace of amber beads protects the wearer 

 against secret poisoning, sorcery, and the evil eye. It 

 is first mentioned by Homer, and beads of it were worn 

 by prehistoric man. Six hundred years B.C., a Greek 

 observer (Thales) relates that amber when rubbed has 

 the power of attracting light bodies. That observation 

 is the starting-point of our knowledge of electricity, a 

 name derived from the Greek word for amber, " electron." 

 In Latin, amber is called " succinum." By heating in 

 oil or a sand-bath, amber can be melted, and the softened 

 pieces squeezed together to form larger masses. It can 

 also be artificially stained, and cloudy specimens are 

 rendered transparent by heating in an oil-bath. 



Amber is the resinous exudation of trees like the 



