MEMOIR ON BOSTON HARBOR. 96 



Of all the charts previous to that of Commodore Wadsworth, it may be said, at once, 

 that they appear to be copied from the survey of Dcs Barres, or of each other more or 

 less, and that, owing to a want of minuteness and of specific description, it is impossible 

 to glean from them more than one or two facts of importance to bo mentioned hereafter. 

 This is not a matter of great regret, since it was not till after 1817 that the Milldam was 

 built, the mill-pond filled up, and large portions of the flats inclosed in South Bay and 

 elsewhere, all of which, together with the numerous constructions on the harbor front 

 on both sides, have been the means of promoting, and of facilitating the natural causes of 

 change in the channels. 



If the means of accurate comparison were at hand, it would undoubtedly be seen that 

 the alterations during the first thirty-four years after the close of the Revolutionary War 

 were very much smaller than during the second period of the same duration. From 1783 

 to 1817, the circumstances, or state of things, remained nearly the same; with the year 

 1817 commenced those great enterprises which, while they mark the growth and pros- 

 perity of the city, have essentially affected the condition of the harbor. In the first pe- 

 riod, whatever deterioration took place was due principally to the operation of natural 

 causes unaided, or to the laws of tidal deposit controlled by the natural form of the 

 shores. In the second, those causes, and the cases under them, have been multiplied 

 and assisted by numerous artificial constructions. 



The comparisons with the chart of Commodore Wadsworth, made in 1817, from an 

 actual survey by himself, furnish very valuable information. 



The life of this officer, every passage of which is stamped with honor and usefulness, 

 having but just been brought to a close, his work ought not to be mentioned without 

 a passing tribute to his memory. Having had the pleasure to sail under his command, 

 and to be associated with him confidentially in important and interesting affairs, I knew 

 him well. He was possessed of a simple uprightness of mind, and zeal and fidelity in 

 the performance of his duty, which give a high authority to whatever came from his 

 hands. In bearing testimony to these intrinsic qualities of his character I am performing 

 a most grateful duty. 



The most useful information obtained from the comparison of the Coast Survey chart 

 of 1847 with the chart of Commodore Wadsworth, relates to the diminution in the 

 breadth of the channel between Bird Island and Dorchester Flats. 



On the chart of the Commissioners it will be seen that there are four cross-sections. 

 The lines of these sections have been transferred to Wadsworth's chart, and the breadths 

 measured between the six-foot and the fourteen-foot curves. The first of these curves, 

 it may be observed, cannot be defined so accurately on the old as on the new chart ; the 



