PBEFACE 



THE time may come when there will be no portion of 

 the earth's surface that has not been surveyed and 

 explored by man. 



The work of enterprising travellers has now been 

 carried on within a measurable distance of the North 

 Pole ; the highest mountain ranges are gradually 

 succumbing to the geological surveyor ; the heart of 

 Africa is giving up to us its secrets and its treasures, 

 and plans of all the desert places of the earth are 

 being made and tabulated. 



The bottom of the deep sea was until quite 

 recently one of these terras incognitas. It was re- 

 garded by most persons, when it entered into their 

 minds to consider it at all, as one of those regions 

 about which we do not know anything, never shall 

 know anything, and do not want to know anything. 



