SCHUYLKILL PERMANENT BRIDGE. ^5 



agonal ; the salient angles acute ; and pointing up and 

 down the stream.* 



The report also shews, how little service was afford- 

 ed by our most ingenious mechanics, out of the line of 

 their several trades. With the best dispositions, many, 

 as well mechanics as other citizens, suggested remedies 

 for misfortunes, or supposed guards against them. 

 Some assisted in executing their ideas in both dams, 

 but not a solitary attempt succeeded. The Company 

 are not the less obliged; nor is it any reflection upon 

 them, as they had as little experience in such undertak- 

 ings, as those whose duty compelled bold and hazard- 

 ous measures, on which, even professional men, versed 

 in hydraulic mechanism, would not have risqued their 

 chai'acters. 



* Hemlock timber^ (Pinus Abies Americana^ Lin.) had near- 

 ly defeated the eof^^crn d'aw : much of it was used, on account 

 of its cheapness. But it always gave way, when hard pressed j 

 and its failure, at sevei-al critical times, was nearly fatal'4 The 

 belts (which serve to a daiyi^ the same purposes as hoops to a 

 -cask) frequently broke ; owing to their being of this wood, and 

 flinty, or curly, in spots. Straight grained hemlock^ entirely free 

 from curl ox flinty is seldom to be found ; though some varieties 

 are better than others. But this timber never should be de- 

 pended upoti ; either for strength, or durability'. It was ex- 

 cluded from the xUesterji dam. Some hemlock is veiy durable ; 

 but the appearance of this wood, is so generally alike, that it 

 is imprudent to risque the chances of hitting on the kind re- 

 quired for lasting, or strength. Perhaps there may be some 

 stages of growth, or time of felling, as it is with other woods, 

 tnore or less favourable to durability. 



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