CCxliv GENERAL SUMMARY OF SCIENTIFIC AND 



of sediment from the current has so filled the interstices as 

 to sink them so that they rest upon the bottom. Each mat- 

 tress is not only fastened to others adjacent and to the piles, 

 but it is anchored in its place by a layer of stone, and the 

 sediment continues to gather in upon them until they be- 

 come more solid and enduring than any part of the natural 

 bank. When completed, the wall of mattresses will perfectly 

 protect the row of piles from the current, while the piles id 

 turn serve to hold the mattresses in position ; and the whole 

 will be finally covered with a firm stone paving. The outer 

 ends of the walls, where they are exposed to the sea, will be 

 constructed of broader and stronger mattresses, supporting 

 solid and durable works. It will be the work of years to 

 complete the whole structure ; but its benefits will begin to 

 be manifest directly, for the channel will rapidly deepen as 

 fast as it is confined within the walls. It is calculated that 

 these will have been so far completed at the close of 1875 

 that the largest ships ever seen in New York harbor can 

 enter the South Pass at any time and proceed without delay 

 to New Orleans. A board of eminent engineers, invited by 

 Captain Eads, with the approval of the President, to exam- 

 ine and pass judgment upon his plans, has, after careful con- 

 sideration of the subject in all its details, emphatically in- 

 dorsed the feasibility of the undertaking. 



The government operations at Hallett's Point for the re- 

 moval of the obstruction to entering the East River by way 

 of Long Island Sound are fast approaching completion. The 

 work, which is under the superintendence of Captain W. H. 

 Heuer, United States Engineer, was begun in 1869, and has 

 cost up to the present time about $750,000. After a tedious 

 labor of nearly six years, the task of excavation was com- 

 pleted about last July, and the secondary work of preparing 

 for the grand blast is now going on. The excavation ex- 

 tends under two and a half acres of gneiss rock vertically 

 stratified. Starting from a main shaft thirty-four feet below 

 mean low water, ten main headings, sloping down to fifty- 

 two feet below mean low water, have been extended out to 

 an average length of 250 feet each. The height of these 

 main headings varies from eight to twenty-two feet, with an 

 average width of fourteen feet. From the main headings 

 intermediate headings have been cut, and at uniform dis- 





