^§ 



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 agratifig, (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 ri\'er, or the grating, prepared for it. 



The coffer dam for the -western pier^ was composed 

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

 Q?\\tdL main piles ; and between these, less, or sheet piles, 

 were driven. The ranges were nine feet from each 

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



several feet larger than that of the lower course of the 

 masonry of the pier. Tliey were connected by cross 

 ties placed horizontally ; and the space between them 

 was 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 Jilling, so as to exclude and resist all access of wa- 

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

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

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

 the heavy rain of a pov/erful pile engine. They were 

 neatly worked and jointed , and united with each other 

 by tongues and grooves. The ranges were secured by 

 jiorizontal frames of large timber, well strapped; called 

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

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

 yjf/e^ between them, were alike in both ranges; and con- 

 nected with each other, as well as with the gratings and 



