SCHUYLKILL PERMANENT BRIDGE. 



61 



The under leakages were highly alarming and ceaseless. 



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

 It was knov/n 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 ; v/hich was 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, witbout 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 very percep- 

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

 so that, in a few days, either Clijmer''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 ahvays 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 onlv meritorious in their motive, and fycilitated the la\ - 



