36S Transactions of the Canadian Institute. [Vol. VII. 



General Changes of Level of Land and Sea. 



The primary object of m)- three visits to the West Indies and to the 

 Central American region, and another to be begun in a few days, has 

 been to carry on my investigations of the great changes of level which 

 have occurred in late geological times, for there one finds the most com- 

 plete evidence at present obtainable. In visiting the Windward Islands, 

 I wished to extend the observations made elsewhere bearing upon the 

 time of the great earth movements, and in doing so I had to irvestigate 

 the geological formations, the results of which have been published in 

 papers mentioned in the foot-note. Besides the geographical descrip- 

 tions, with some geological results given here, I have included the charts 

 of the region from which much more information can be gathered.* On 

 these I have also drawn certain lines of soundings to bring out the 

 drowned valley-like features. 



While a somewhat less elevation of the region would connect the 

 more northern of the Windward Islands, as we have seen, a rise of 3,600 

 feet would unite Dominica and Martinique (by way of the banks shown 

 on map, Plate C), with an embayment between them reaching to a 

 depth of 6,600 feet, miles within the line connecting the two islands. 

 An elevation of 3,300 feet would bring the ridge between Martinique 

 and St. Lucia to the surface, with another deep indentation to the west, 

 a tributary of which heads in an amphitheatre, incising the island mass 

 north-west of St. Lucia to a depth of 6,624 feet, within the line where 

 the shelf is sunken only 600 feet. Between St. Lucia and St. Vincent, 

 the connecting ridge is mostly within 1,200 feet of the surface, except 

 for about five miles where the channel across the col reaches to a depth 

 of about 3,000 feet below sea level. From this point the drowned 

 valley rapidly deepens to nearly 6,600 feet within the line of the islands. 

 The deepest part of the drowned valley crossing the ridge between St. 

 Vincent and the Grenadines is only a mile wide and does not exceed a 

 submergence of 1,300 feet. The Grenadine banks, really a submarine 

 tableland, are covered by 100 or 150 feet of water, and the western slopes 

 show the indentations, amphitheatres or cirques reaching to the same great 

 depth, and still further away the soundings suggest that the submerged 

 Antillean plateau in part rises more than 9,000 feet without quite 

 reaching the surface of the sea. The cirques or amphitheatre-valleys 

 on the eastern sides of the islands have not been so fully shown as on 



* The charts are a reduction of Chart 40, U. S. Hydrographic Office. The various larger charts ot 

 the different islands should be consulted. 



