5g A STATISTICAL ACCOUNT OF THE 



calculated for the depth, or raised upon as it sinks with 

 the weight, it finally arrives on a level bottom, or bed, 

 (which is indispensable) or on 2i gratings (supported by 

 piles, driven into a pervious and deeply covered bed,) 

 accurately prepared for its reception, and permanent 

 station. When it is thus fixed, the sides of the box are 

 detached, and the masonry is exposed : the bottom of 

 the batterdeau remains under the masonry, either on the 

 bed of the river, or the grathig, prepared for it. 



The coffer dam for the western pier, was composed 

 of two ranges of piles; some, much larger than others, 

 called ?nain piles ; and between these, less, ox sheet piles y 

 were driven. The ranges were nine feet from each 

 other; embracing, within the interior range, an area, 

 several feet larger than that of the lower course of the 

 masonry of the pier. They were connected by cross 

 ties placed horizontally ; and the space between them 

 Vv'as filled with loam, or earth, and called puddle; con- 

 solidated from the bottom, or bed, of the river, to a 

 height above the tide ; and forming an embankment of 

 this filing, so as to exclude and resist all access of wa- 

 ter. The piles were about 42 feet long; and, being 

 sharpened, and shod with iron, at the lower ends, were 

 driven (where the cover on the rock would admit) by 

 the heavy ram of a powerful pile engine. They were 

 neatly vrorked and jointed, and united with each other 

 by tongues and grooves. The ranges were secured by 

 horizontal frames of large timber, Avell strapped; called 

 belts, of the shape and figure of the dam ; which had six 

 sides. These belts, which were double, to receive the 

 piles between them, were alike in both ranges; and con- 

 nected Vv'ith each other, as v/ell as Avith the gratings and 



