10 INTRODUCTION 



phosphorescent animals. Owing to the lack of 

 sunlight, there is an almost entire absence of 

 vegetable life in the deepest parts of the ocean. 

 Sir John Murray, the eminent oceanographer, calcu- 

 lates that on more than nine-tenths of the ocean 

 floor there are no forms of vegetation of any 

 kind. 



Our knowledge of the ocean and the ocean 

 depths is still far from complete. So many 

 difficulties exist that progress must necessarily be 

 slow. These difficulties arise principally from the 

 fact that, in the majority of cases, the observa- 

 tions are necessarily indirect. At the surface of 

 the ocean direct observation is possible, but our 

 knowledge of the conditions prevailing in deep 

 water, and of all that is there taking place, is 

 almost wholly dependent on the correct working 

 of instruments, the action of which at the critical 

 moment is hidden from sight. Dredgings and 

 soundings, however, reveal many important details, 

 and divers are able, from time to time, to add to 

 our knowledge of marine life and conditions. 



When the cinematograph first made its appear- 

 ance no one dreamt of its enormous and far- 

 reaching possibilities as a scientific instrument. 

 Essentially, at the outset, intended to provide a 

 cheap form of amusement, it was not long before 

 it was seen that the cinematograph could be used 

 not merely for purposes of entertainment, but 

 also for those of instruction. At the present time 

 we are beginning to understand a little more 



