Show t I 1 sh 1 11 Z A landing a giant T tuna una in nova scotia prepared by nat onal geography Geo graph c soc ety wash agton D C ce cc S ONE stands on the sea AS A shore at the full of the tide and looks out over the swell ing floods surging in from th the e distant horizon his feet are on the threshold of an enormous empire so sor vast in extent and population that the achievements of the haughtiest rulers of mankind are dwarfed by comparison though fleets sail over its depth they make no significant imbres sion upon this immense realm the subjects of this empire swarm through the waters in my reads totaling far greater numbers than all the life of the continental world in fact scientific in eions indicate that the oceans were the original abode of life on the globe and that the continents were peopled from that inexhaustible res geologists believe that the depres now occupied by the oceans have been located in approximately their present positions during the entire history of the earth and that the foundations of the land masses likewise have been situated nearly as they are at the present time but during the great geological periods the ocean has repeatedly invaded their edges and even their interior basins sometimes to an enormous extent forming shallow seas thus all the continents of the world are bordered by a strip of shallow sea the continental helf chelf which slopes gradually from the coast to depths varying from to 1000 1 fathoms at its outer edge be yond this limit there is usually a more rapid gradient to the main maln floor of the ocean the continent al slope this world wide shallow strip is of major importance to the life of the seas north atlantic shelf this article deals especially with the mollusks mol luks and other small crea tures inhabiting the continental shelf which borders the atlantic coast of north america from nova scotia to new york and includes the extensive new england fisher ies A most remarkable stretch of shore this is its southern half is of comparatively even contour but beginning with the region of cape hatteras the coast to the north ward has subsided and is indented with deep bays and irregularities finally terminating in the long ing and tapering indentation of the gulf of maine the latter is the most noteworthy feature of the coast its wide mouth being guarded on either hand by cape cod and cape sable and its inner reaches narrowing to a double apex in the bay of fundy all this northern half of the at lantic alantic seaboard is a succession of drowned valleys and its topography and geological history indicate that it has subsided beneath the waves of the sea during relatively recent times on the other hand the even outline of the coast from hatteras south to florida shows no evidence of such sinking the oceanic shelf to the fath om am line widens rapidly to the north ward reaching its greatest extent off the gulf of maine where it is approximately miles wide the central floor of the gulf of maine is an ancient river valley to which the river systems represent ed by thoe now existent contri contribute but ed their drainage to be emptied in to the prehistoric sea by a single channel and mouth still traceable on the sea floor at the edge of the continental shelf throughout this extensive and comparatively shallow oceanic margin we well 11 illuminated by the sun s rays conditions are f favorable avo rable for an enormous development of the marine plants on which sea am ani mals feed namely the microscopic diatoms one celled algae and the larger seaweeds nursery for food fishes here numerous streams empty their loads of silt rich in nitrates phosphates and other chemicals needed for plant food the strong tides rushing into the narrowing channel from the open sea keep the water stirred with up currents plentifully supplied with oxygen hordes of small crustaceans the copepods feed upon this plant life at certain seasons they swarm in these waters in numbers so vast that they give the sea a reddish olor for miles these tiny creatures are rian in oils and are greedily devoured by large schools of mackerel herring alewives and shad bluefish cod hake and haddock pursue and de bour the smaller fishes and even the huge fi finback and humpback whales do not disdain to feed upon the herring thus the shallow banks oft off new england especially georges and browns banks at the entrance to the gulf of maine as well as the grand banks of newfoundland farther away form a veritable nursery for the important food fishes of our coasts and thus connect man kind by an interlacing food chain with the microscopic micro copic plant life of these shallow waters the evolution of the animal world as we know it would have been impossible had these primitive plants not come into existence from such forms also all the higher land plants of the world nate the zone As the open seas were peopled from the oceanic shelf so the fresh water streams and swamps received parts of the overflow countless cies found food and a measure of or safety from enemies by creeping into the area between the tides where they acquired resistance to exposure to the open air at the intervals of low water here a rapid evolution took place so that the zone became densely populated with life finally from fresh water swamps on the one hand and from the upper P parts arts of the marine tidal zone on the other first plants and then animals in als invaded the land itself and produced the highly specialized types that now reign over it north of cape cod the coast of new england is predominantly high and rocky beginning with the head lands of nahant jahant marblehead and cape ann north of boston the cliffs are at first isolated to local regions with intervening stretches of sandy beaches and flats but from port land in casco bay northward the coast is an almost unbroken sue suc cession of granite cliffs sloping rock ribbed promontories and re entrant bays and harbors with oc cc cas ional beaches the tidal waters flowing from th the open sea are gradually confined by the narrowing outline of the gulf of maine which forces them to a pro gres increasing height and reach a climax in the bay of fundy from massachusetts bay north to portland the tide rises nine feet it continues to increase northward until it becomes 18 feet at eastport East port and 37 to 48 feet at the ends of the two tapering horns which terminate the bay of fundy here too there are interpolated stretches of beaches flat points and swampy meadows and these are entirely covered at high tide naturally the width of the tidal zone on the side of a vertical cliff is measured exactly by the vertical rise and fall of the water for ex ample the cliffs that surround bliss island at the entrance of bay are exposed for 22 feet from the top of the barnacle frieze that marks the high tide limit to the water level at low tide crowded with life this region between the tides is teeming with life both plant and animal in crowded array on the vertical granite walls of bliss island the various species are arranged in overlapping zones with the bous white band of rock barnacles below this the rock weeds hang in thick gracefully festooned clusters down to the low water mark concealed beneath the rockweed and succeeding the base of the barnacle zone the rocks a are r e covered with a dense layer of young black mussels among them are closely crowded groups of the common dog whelk feeding upon the mussels and laying their graceful vase shaped egg cases tinted rose and yellow in mosaic like patches in the crevices the latter mollusks secrete a pur pie dye formerly used by the in deans for coloring their deerskin garments they are related to the murex of the phoenicians Phoenicia ns from which that people derived the fa royal purple later arrogated by the roman emperors for their personal ue the dog whelk has a thick shell with a characteristic spindle shaped opening it is extremely variable in color size and sculpture along the new england shore the common periwinkle creeps everywhere over the rockweed from the low water mark to the highest part of the barnacle zone and even upon the bare rocks rock far above it this remarkable sea snail can stand exposure to the open air longer than any other marine creature of the northern coast it is in a transitional state of evolution toward terrestrial life for its gill seems to be on the point of being replaced by a lung it has a very wide range being found on both sides of the atlantic in eng land it is the common winkle sold in markets |