THE NATIONAL GEOGRAPHIC MAGAZINE 



517 



and alas, the untiring foe drives a salient 

 into the lines of the land and uses the 

 booty captured in his next drive. The 

 salient is a bay or cove,, and the wings are 

 the headlands that bound it. 



If one thrust be not too bitter, or if the 

 retreating shore-line finally reaches a sec- 

 ondary line of defense on firmer ground, 

 the enemy is held ; otherwise it drives 

 around the headland on all sides ; and 

 thus do "pulpit" or "chimney rocks" be- 

 come lone outposts. 



WHEN THE SEA ENCOUNTERS CROSS-EIRE 

 RESISTANCE 



It often happens, however, that when 

 the thrust of the sea becomes too deep, 

 the flanks of the attacking forces are ex- 

 posed to the cross-fire resistance of the 

 headlands, and finally reach a degree of 

 penetration where they cannot maintain 

 communications, and their attack comes 

 to a standstill. In such a case we have a 

 deep bay where the rushing waves of the 

 sea lose their force before they sweep the 

 inner shore-line. 



One does not have to study the war- 

 fare waged by the sea very long before 

 discovering that it not only uses "pincer" 

 tactics, but that it also makes use of min- 

 ing operations. Sometimes it finds that 

 its most powerful onrushes are dissipated 

 by the resisting power of a great head- 

 land, as the dew is dissipated by the morn- 

 ing sun or the darkness by the light of 

 day. 



With boulder and shingle the waters 

 drive furiously at the base of the cliff, 

 tearing away its foundations inch by inch 

 and foot by foot until a soft spot is un- 

 covered, and the sea enemy finally under- 

 mines entirely the great structure of 

 defense. Then with the hydraulic pres- 

 sure of an imprisoned wave it heaves for- 

 ward, and the rocks above have no alter- 

 native but to tumble helplessly into the 

 maw of the liquid host, to become projec- 

 tiles in the sea's further assaults. 



Often, too, the rushing waves find a 

 weak link in the armor where one ledge 

 of rock overlies another, with gravel or 

 clay between. Yard by yard they wear 

 out this grouting material, and a sea cave 

 is the result. 



The ledges which constitute the roof 

 and the floor, respectively, have a dip to- 



ward the sea, and as the waves rush in 

 they come nearer and nearer to the sur- 

 face, until finally they break through at 

 some joint in the roof, and we have the 

 spouting horn — a trumpeter of Xeptune 

 who gives the gage of further battle with 

 each flooding tide. 



At still other places the waves drive 

 back the softer shore and bare a long 

 stretch of adamant on each flank. And 

 then it comes to a spot in this flinty head- 

 land that is weak, and cuts its way 

 through, making a graceful arch of a 

 wonderful, wave-hewn natural bridge. 



The tremendous power of the sea in 

 utilizing the boulders it has wrested from 

 the land in its return to the attack sur- 

 passes belief. Huge rocks, weighing sev- 

 enty-five tons or more, have been moved 

 by the power of the waves. 



THE 42-CENTIMETER SHEIXS OE THE SEA 



Driving the big boulders up against the 

 cliffs as though from a giant catapult, 

 these 42-centimeter shells are finally worn 

 down into cobble-stones, then into peb- 

 bles, then into sand, and at last into silt, 

 which, caught up by the undertow, is 

 borne along and out to sea, a bit of land 

 forever in the prison-camp of the ocean. 



As a result of the terrific grinding of 

 the glacial ice of ages agone and in the 

 following centuries under such methods 

 of attack as have been broadly sketched, 

 the Maine coast beyond Portland has be- 

 come a series of gulfs and bays and head- 

 lands, with islands and rocks without 

 number as the observation posts and first- 

 line defense against the sea. 



From Portland to Newburyport the 

 bold cliffs gradually lower their towering 

 forms and beaches and broad bays ap- 

 pear (see page 523). From Newbury- 

 port to Woods Hole is about eighty-five 

 miles in a bee-line, but if you follow the 

 shore around Cape Cod Bay and down 

 along Nantucket Sound it is some three 

 hundred miles. In that stretch of coast- 

 line one might see fairly good types of 

 all the shores from Greenland to Florida. 

 There may not be fiords like those of the 

 far north or swamps like those of Vir- 

 ginia, Georgia, and Florida, but there are 

 enough shore-line features to fascinate 

 any pilgrim who would wander that way. 



