108 J. D. Dana on the origin of some of the 



the level of the water. But on tliis point we have no facts, since the 

 wells over the plain have never been sunk so deep as to reach such a 

 layer, nor even below a depth of forty feet. If the Beaver Pond de- 

 pression was once, as supposed, a central basin of the harbor, it is 

 likely that there is such a layer beneath. 



Some facts respecting Artesian Wells are mentioned beyond, 



2. Hard-pan of the harboe. — The following observations on the 

 hard-pan beneath the harbor consist mostly of information obtained 

 through the driving of piles, and the sinking of Artesian Wells. For 

 the facts derived from pile-diiving I am indebted mainly to Mr. C. R. 

 Waterhouse, whose occupation has given him numberless opportuni- 

 ties for observation. 



a. At the head of the bay, near the foot of Greene street, in preparing 

 the foundations for the Gas Works, a hard-pan layer was found at a 

 dejjth of 31 feet below the level of the sea; the overlying material 

 being harbor mud. The layer was 3 feet thick. On driving through 

 it, by way of experiment, the piles went down through 4 feet of mud 

 or loose sand, without finding another hard layer. 



h. In the construction of the Chapel street bridge across the mouth of 

 Mill River to Grape Vine Point, a little south of the Gas Works, the 

 piles, starting from mean-tide level, penetrated 33 feet of mud and 

 struck the hard-pan. The layer was so hard that the piles made but 

 au inch or two at a stroke, and with 54 strokes did not go through it. 



c. At the steamboat dock, 120 rods farther south, the piles passed 

 through 25 or 20 feet of mud before reaching the hard-pan. 



At the end of Long Wharf, two-thirds of a mile outside of the old 

 coast line, and near the deep-water channel of the bay, the liard-pan " 

 was reached at a depth of 45 feet below mean-tide level; 13 of the 45 

 feet being water, and 32 mud. 



d. In the construction of the new Long Wharf for the Canal railroad, 

 situated only twenty rods east of the old Long Wharf, and extend- 

 ing to the same deep-water channel of the bay, the piles, at the ex- 

 tremity, and for the greater part of its length, as I learn from IMr. 

 Yeamans, the Vice-President, were driven down 43 to 45 feet below 

 mean-tide level, the longest being those between its middle and the land. 

 In driving other piles over the old Canal basin (which adjoins the wharf 

 on the north) it was found that a region of very deep mud extended east- 

 ward not far outside of the present line of yards and buildings, Avhich 

 was evidently the former submarine bed of the old East Creek chan- 

 nel (whose waters it will be remembered, had their discharge into this 

 Canal basin at its head, just east of the old Long Wharf, and close 



