SCHUYLKILL PERMANENT BRIDGE. 51 



The under leakages were highly alarming and ceaseless. 



another day's work would have defeated the whole enterprize. 

 It was known that nothing but actual perception of the con- 

 sequences, would bring conviction ; which all reasoning (re- 

 sisted by the strong desire to reach the rock) had failed to 

 produce. Several of the stoutest labourers were set to work, 

 with a view to dig a pit, to the rock ; which v/as not more 

 than 3 or 4 feet from the then surface. They had not pierc- 

 ed the mud above half its thickness, before a column of wa- 

 ter, copious and alarming, suddenly gushed up. This pro- 

 duced an immediate conviction, of the unjustifiable hazard 

 of any farther attempt to bare the rock : and the factitious 

 foundation, being, without farther hesitation, agreed to, was 

 forthwith commenced. The principles on which this occur- 

 rence was predicted, appeared to be proved ; not only by this 

 specimen of the effect of admitting even partial avenues for 

 the water, but in the progress of the masonry. — After the 

 foundation was completed, the leakages lessened veiy percep- 

 tibly. As the work proceeded daily, the leaks decreased: 

 so that, in a few days, either Chjmer'^Sy or the chain pumps^ 

 could free the dam ; and at length pumping was intermitted, 

 for long intervals, entirely. Thereafter to the close of the 

 work, the chain pump was sufficient; and only occasionally 

 employed. The water flowed round the work, during the 

 time of laying a few of the first courses of the masonry ; but 

 afterwards it remained below, and was harmless and manage- 

 able. — Some advantage, no doubt, accrued, by the compactness 

 of the foundation filling the dam. But there always had been 

 dangerous and constant leaks above this; which, until the 

 pressure of the external head of water was fairly conquered, 

 and entirely overbalanced, by the additional and daily en- 

 creasing weight of the masonry, never ceased to flow, copi- 

 ously and perilously. The exertions of the Committee were 

 not only meritorioir? in their motive, and facilitated the lay- 



