i05 [52] 
i'atcly, full tide is four feet three inches six-tenths higher, relatively, 
than high water in Buzzard's Bay. 
A canal may, therefore, be excavated and drained to the low water 
mark, and carry eiglit to nine feet, and sometimes twelve feet, 
filled, continually, by the tide, and kept full by the gates of the locks 
which must occupy its entrances. The northern entrance, from the 
Bay, must be protected by a break-water, or pier, forming, to som© 
extent, an artificial harbor. 
Examples of this kind of construction arenutnerous in Europe; and, 
in this Bay. we have one to tlie extent of several hundred feet at Cape 
Ann. The bottom off Sand\^ ich is found to be good anchoi'age — three 
and a half fathoms are found at one-third of a mile, or three fathoms are 
found 250 fathoms from the shore. Immediately within the beach it 
would be easy to excavate, in the Salt Marsh, a basin, for shipping to 
wait a favorable wind, and, by means of a dam near the mouth of 
Scusset Creek, to include a body of water so extensive as to supply the 
lockage without materially affecting the level or depth of the canal. 
To render this passage at all times useful, it will be necessary to 
enter and leave it at all times of tide. This can only be provided for 
by cari'ying the lock out beyond low w ater mark, placing it in depth 
sufficient to float a vessel into it at low waUr. This lock must, there- 
fore, be of double the usual depth, or there must be two of them in 
succession. The construction of locks, in a situation thus exposed to 
the action of the sea, is no doubt attended with some difficulty. The 
usual resource of the Coffer Dam is impracticable here. In two simi- 
lar situations in Scotland, (except in exposure to the open sea) they 
projected a mass of earth, and excavated for the lock therein. But 
here the very nature of the adjacent country forbids this method as 
w ell as the "waves of the ocean. In one of the reports which had been 
made, it was contemplated, as most expedient, to line the lock w itli 
plank, and make it tight by caulking: but, although this might answer, 
and be easily executed, if tlie lock is placed wholly above water at low 
tide, and consequently operative only at the moment of high tide, it 
would not be conveniently and securely done for a deep lock. Ce- 
mented w alls cannot be built under w ater. Perhaps there remains, 
therefore, but one method, which is to build the lockabove w ater wholly, 
and place it between the strong rough walls, which should be 
previously built to receive, sustain, and protect it. 
If this were to be the mode of construction, and rvood the material, 
the next question would be, both how it should be made dui-abie, strong, 
and perfectly tight: the answer would be, that this structure should be 
built over the situation prepared for it, and lowered into it complete 
when the previous arrangements being made, it might be permanent- 
ly secured, or it might be built like a vessel on shore, and launched, 
&c. The manner of constructing it for tightness and durability would 
be, in preference, the new method of sliip building in England, by 
successive layers, transverse to each other, interposing tarred canvass 
or paper, the materials theu become posited in their greatest strength, 
pei-pendicular to the fibre, while tlie resinous substances exf:lude thp 
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