OCCULTATION 



SB I 7 



OCEAN 



neeessarilv formed. The power that 



tini -1\ iliMiled charcoal has for ab- 



gases ia made use of fur dis- 

 infect inn purposes. &ee Absorption. 



Occilltation. In nstr..n.im\. 



the eclipse of a star or plunot by 



in or another planet. Occuf- 



tiition oliM-rvations are now chiefly 



used for determination of the 



- angular diameter. See 

 BettpM. 



Occultism (I ..at. occultua, hid- 

 l .-mi applied to any theories, 

 ilo.-trincs, arts, or practice* dealing 

 with al !<_ ed phenomena not ex- 

 plained by physical science, but 

 attributed to supernatural or 

 non-natural causes. See Divina- 

 tion; M:i'jic; Necromancy ; Spirit 

 uali*m : Thcosophy; Witchcraft. 



Occupancy. Term used in 

 Kiidish law. It means taking pos- 

 session of something, whether land 

 or chattels, which belonged to 

 nobody. It was only recognized as 

 a legal title to land in the case of 

 tenancies pur autre vie (old Fr., for 

 the life of another). When an 

 estate was granted to A for the 



life of B, and A died before B, 



anybody who -i.ulil it rut K in ttl "' 

 occupy the land miuht ke<p it f'-r 

 the rent <.f tin- life ..( II. Hut by 

 the Will* Act, I vis. this ban been 

 altered. A can now devise the 

 estate by hU will ; or, if he doe* 

 not so deal with it, it passes with 

 the rest of his property to his 

 executor or administrator. With 

 regard to chattels, anybody aut hur. 

 ised by the crown may seize and 

 keep goods belonging to an alien 

 enemy. In this way prizes cap- 

 tured by privateers became law- 

 fully theirs. Wild animals and 

 fish at sea also become the pro- 

 perty of those who capture th-m. 



Occupation. Lc^il term hav- 

 ing two meanings : (i) a trs/ie or 

 means of getting a livelihood, e.g. 

 the occupation of a carpenter. In 

 a few legal documents, the princi- 

 pal of which are bills of sale and 

 the documents relating to mar- 

 riages, it is essential that the par- 

 ties shall be described by reference 

 to occupation, (ii) Possession of 

 land or chattels. 



OCEAN AND OCEANOGRAPHY 



Marion I. Newhigin, D.Sc., Author of Modern OeotfrAphy 

 This Encyclopedia contains articles on the world's oceans and seas, 

 e.g. Atlantic ; Indian ; Pacific ; Mediterranean ; North Sea, etc. See 

 also A rctic Exploration ; Challenger ,- Marine Biological Research 



Oceanography is the science 

 which deaU with the form of the 

 ocean floor, the nature of the sedi- 

 ments covering it, and the composi- 

 tion, temperature, and movements 

 of the contained w aters. 



The elaborate series of soundings 

 carried out by deep-sea expedi- 

 tions have demonstrated that the 

 primary feature of the earth's relief 

 is the existence of depressions, the 

 ocean basins, and of elevations, 

 the continental platforms. But the 

 latterdonot, in their entirety, form 

 land areas, for their margins tend 

 to be submerged, producing the so- 

 called continental shelves. In other 

 words, there is more water than 

 can be held in the ocean basins, 

 and the surplus overflows the en- 

 ilinllinir lands. That the continental 

 shelves are really part of the con- 

 tinental platforms is suggested, 

 among other point*, by the fact 

 that the relief features charac- 

 teristic of land surfaces, such as 

 river valleys, are often prolonged 

 across them ; that their surface 

 tends to be covered by detritus 

 obviously derived from the ad- 

 jacent land mass, and that there 

 is sharp and sudden change of 

 slope at their seaward edge, where 

 the ocean floor plunges abruptly 

 down to the great depths. On the 

 other hand, the ocean basins are 

 covered by a depth of water no- 

 tably greater than that overlying 



the continental shelf ; their de- 

 posits are purely marine in origin, 

 or at least their land origin is not 

 apparent ; their relief is markedly 

 different from that of land surfaces 

 or of the continental shelf. 



The width of the continental 

 shelf varies in different parts of 

 the world ; broadly speaking, how- 

 ever, 50 m. marks the limit of 

 breadth. There is variation in the 

 depth of the water which covers.it, 

 but as a general rule the sudden 

 steepening which marks the transi- 

 tion between shelf and ocean basin 

 occurs at or near the 100 fathom 

 limit. Some 10,000,000 so. m. of 

 the sea floor aie reckoned to be 

 covered with such shallow water, 

 and thus to rank as part of the 

 continental shelf. Put in another 

 way, while the ocean area includes 

 about 143,000,000 sq. m. as con- 

 trasted with a land area of 

 54,000,000 sq. m., only some 

 133,000,000 sq. m. constitute the 

 o-.ean basins proper. 



Ocean Piains and Deeps 



The oceans are not great uniform 

 hollows ; although their form is 

 markedly different from that of the 

 land masses, they have a relief of 

 their own. In most cases the floor 

 over vast areas seems to be an 

 almost regular plain, but in places, 

 especially in the Pacific Ocean, 

 there are depressions which sink 

 very notably below the general 



level, and unually have more or 

 less steep sides. Such depressions 

 are called deeps, a deep being 

 denned as an area in wln-h tin? 

 <lcpth exceeds :(.'< 

 Elsewhere, especially in the At- 

 lantic, great swells rise from the 

 ocean floor, forming areas of rela- 

 tively shallow w.i i eleva- 

 tions are called rises, and are de- 

 fined as areas in which the depth 

 is 2,000 fathoms or less. Contrary 

 to what might be expected, the 

 deeps tend to occur near the con- 

 1 1 margins, while the rises 

 are often far from laud. 



Volcanoes on the Ocean Floon 



Active volcanoes often occur on 

 the ocean floors, so that v> 

 cones may be built up to a height 

 sufficient to iring their surface to 

 sea level, or even above it. Such 

 volcanic cones arc commoner in 

 the Pacific than elsewhere, and 

 they are more abundant in the 

 deeper western than in the shal- 

 lower eastern areas. Now, since 

 volcanoes, whether on land or in 

 the sea, are associated with earth 

 movements, being, like earth- 

 quakes, but obvious and visible 

 signs of great and deep-seated 

 changes, it seems clear that the 

 present oceans must be regarded 

 as areas of subsidence, due to the 

 collapse of earth blocks, while the 

 present continents are areas which 

 have either been left standing 

 when other parts collapsed, or have 

 been directly uplifted. 



The period called tertiary by 

 geologists was one in which ex- 

 tensive mountain building took 

 place, and it is natural to associate 

 the great deeps of the existing 

 oceans with the tremendous up- 

 lift of the tertiary mountain 

 chains. It is noteworthy that the 

 Pacific is practically ringed with 

 mountain chains, with which 

 active volcanoes are associated, 

 while the greatest deeps known 

 occur also in that ocean. 



While the composition of sea- 

 water salts remains everywhere the 

 same, the salinity varies greatly. 

 Broadly speaking, the salinity is 

 high where the temjH-rature is high, 

 evaporation great, and the amount 

 of fresh water supplied by rainfall 

 or rivers small, and low where the 

 reverse conditions prevail. On an 

 average the amount of dissolved 

 salts ia 35 per thousand parts of 

 water, but the :u-tual conditions 

 van- greatly in different areas. 



Tcni|>eruine conditions ar- 

 ple\. for both surfaoe conditions 

 .mi I those prevailing at the various 

 depths have to be considered. 

 Broadly speaking, surface tem- 

 peratures ucpend upon sun heat, 

 so that the water Is ice-cold near 

 the poles, and reaches 80' at the 



