520 l 1 . P. GULLIVER — NANTUCKET shorelines 



flowing currents. There are many recorded changes in the form of this 

 point since the beginning of the plans for the improvement of the harbor 

 by the building of the jetties, and during the last 25 years there have 

 been many detailed studies of this region made by the engineers. A 

 study of the changes which can be directly traced to the building of the 

 jetties and the consequent increase of the tidal in and out flow will be 

 very helpful in any discussion of the general method of the formation 

 of these cuspate projections of sand into ba3 7 s. 



One of these changes is due to the fact that the western jetty prevents 

 the movement of the sand from the northern shore of the island out to 

 the end of Brant point; consequently the sand is piled against the jetty 

 on the west side at the bathing beach. From 1881 to 1897 the shore- 

 line on the west side of the west jetty extended 250 feet farther north- 

 ward along the jetty, and from 1897 to 1902 150 feet more. Thus in 

 twenty j^ears there was an extension at this place of 400 feet. Of course, 

 sand has been blown over the jetty and carried along toward the end of 

 Brant point, but the west jetty has prevented the free movement of sand 

 along the northern side of the point. Half way between the western 

 jetty and the end of Brant point the shoreline was cut back during 

 these twenty-one years from 1881 to 1902 100 feet. This was due un- 

 doubtedly to the increased flow of the tidal currents in and out of the 

 harbor between the two jetties. 



Nantucket Harbor 



The point of greatest interest to most people in the study of the 

 changes around Nantucket is the question as to how the movements of 

 sand along the shore will affect the depth of water in the harbor, and 

 what improvements must be made in order to keep the harbor from 

 filling up, so that it can no longer be used as a port. The two jetties 

 built from Brant point and Coatue were constructed to increase the 

 depth of water across the bar at the mouth of the harbor. The jetties 

 have never been completed, and it is decidedly a question how great 

 the increase in the depth of channel across the bar would be if they 

 were completed. The theory of such jetties as this is that the tidal in 

 and out flow, being confined to the narrow channel, will scour out the 

 sand and leave a channel in the runway. As long as the east jetty is 

 uncompleted, it allows the water to go through the gaps, and thus the 

 full strength of the in and out flowing currents is never attained. 



The general conditions of the erosion of the island show that the sand 

 is worn away from the exposed portions and deposited in the quieter 

 waters on the landward side of the island. Great point, Smith point, 



