GEOLOGY OP NORTH ATLANTIC GILLIGAN 211 



That it is the scene of active earth movement at the present time is 

 evidenced by the great earthquake which affected Lisbon in 1755, 

 when the center of the disturbance lay off the coast of Portugal and 

 the waters overwhelmed the quay at Lisbon, drowning some 30,000 

 people. 



Termier lays great stress upon the finding of tachylyte, the glassy 

 form of basalt, at a point about 500 miles north of the Azores and 

 at a depth of about 1,700 fathoms. In dredging for a broken cable 

 in 1898 the grappling irons were found to be scored and scratched as 

 if they had been di-awn over the ragged edges of freshly broken 

 rock, and on one occasion some splinters of the glassy tachylyte 

 were found adhering to the irons. These are now preserved at the 

 Musee de I'Ecole des Mines at Paris. 



As he rightly points out, had this lava been erupted and cooled 

 under atmospheric pressure, then the outermost part would form 

 a thin selvage of glass or tachylyte, but if it had been erupted at 

 the depth where it is now found, the pressure would have been such 

 as to produce some crystalline structure. From the ruggedness of 

 the ocean floor at this point, and the association of tachylyte with 

 what appear to be bare rocks, he deduces a very recent submergence 

 of the area, and also considers that this collapse was sudden. 



From the inequalities in the ocean floor to the south and south- 

 west of the Azores he argues that it is highly probable that a detailed 

 dredging, such as was carried out to the north, would reveal a similar 

 sunken land of recent date — 



and before your eyes would increase then, almost immeasurably, the buried 

 region, the region which was abruptly engulfed yesterday and of which the 

 Azores are no more than the evidences escaped from the general collapse. 



Geologically speaking, the Platonian history of Atlantis is highly 

 probable. 



THE FLOOR OF THE ATLANTIC 



It must be clearly understood that although we have a general 

 conception of the topography of the floor of the Atlantic, yet we have 

 no precise knowledge of the relatively smaller elevations and de- 

 pressions; and if a chart showing the soimdings of the North At- 

 lantic is examined, it will be seen how widely separated these are. It 

 is quite possible that when a sufficient number of soundings are 

 taken it will be found to be as irregular as the land surface, or at 

 least it will be much more ridged and furrowed than any of the 

 charts at present show. 



The main points to be seen at present are two great depressions 

 which run parallel with the coast lines and also parallel to another 

 striking feature — the central ridge or rise which, starting from the 

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