1841.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



75 



attention needed for the highest and widest gates, being that which 

 is requisite to manoeuvre the wickets E or F, a duty for which a mere 

 bov would be piiysically competent. 



The sluice gates used upon the Lehigh descending navigation, as 

 there is no necessity of making them perfectly water-tight, are allowed 

 a plav on each side of half an inch or more, which eirectuai;y prevenU 

 lateral friction; they are generally twenty-four feet wide, formed by 

 •spiking together three successive layers of thick plank, and the lower 

 leaf is strengthened by bolting upon its back a few heavy beams, (as 

 may be seen in the sketch annexed,) which rest their extremities 

 against suitable stops when the gate is up. 



Where the water, violently descending the sluice, leaves the plat- 

 form, it usually excavates the bed of the stream and forms deep water, 

 the sudden entrance info which, of boats shooting down the sluice, 

 would prove very injurious to, or even destroy them, if it were not 

 for the ingenious device called fingers ; tliese consist of the trunks of 

 trees placed side by side, and bolted to heavy subsills, with their butts 

 up-stream, the to]>s freely projecting over the lower sill some twenty 

 feet or more ; they receive in part the shock of the boat in its plunge 

 into the deep water, and by their elasticity ease off its momentum so 

 that it glides down with the swift stream uninjured. This dexterous 

 mode of avoiding concussion is found in practice fully to answer the 

 end for which it was designed. 



For the purpose of guarding the horizontal hinges of the leaves of 

 the sluice gates against obstruction from the deposition of gravel, a 

 glove of plank is ingeniously secured across the hinge by a curved 

 spring; and in contact with this plank glove, the leaf revolves upon its 

 hinges, without the possibility of being impaired in its action by the 

 lodgment of hard substances. 



From the above description and the annexed sketches, which are 

 designed more to develope l/ie principle of the sluice gate, than to 

 display all the details of its construction, it is hoped that the plan and 

 mode of action of the Bear Trap Stuice may be gathered without 

 fuither explanation, and we will now proceed to make a few remarks 

 upon the great usefulness of this inrention. 



UTILITY OF THE BEAR TRAP SLUICE. 



This skilfolly devised hydraulic machine continued in use upon the 

 lower Lebigh — giving perfect satisfaction in practice — from the year 

 1S21 until lb2'.', when the descending navigation upon the main part 

 of the river was abandoned for an improvement which admitted of 

 transit in both directions : though a section upon the former plan, with 

 its Bear Trap Sluices, still forms the navigation for the lumber trade 

 betwen Whitehaven and Stodd.irtsville, a distance of 121 miles, m 

 which by wing-dams, channels, and sluices, a fall of 336 feet is 

 overcome. 



The causes which led to the substitution of a slaekwater for a flash 

 navigation, and the difficulties met and surmoimted by the ingenious 

 and energetic individuals who directed the works of ttie Lehigh Com- 

 panv, are so interesting, that we will make a digression to quote a few 

 more passages from the Company's published "History,"* 



"The bouts used upon the Lehigh descending navigation consisted 

 (if square boxes, or arks, from lii to 18 feet wide, and "20 to 25 feet 

 long. At first two of these were joined together by hinges, to allow 

 llipm to bend up and down in passing the dams and sluices, and ius the 

 men became accustomed to the work, and the channels were strength- 

 ened and improved as experience dictated, the number of sections in 

 each boat was increased, till at last their whole length reached 18u 

 feet. They were steered witli long oars like a raft. Machinery was 



* Id (he nulilialinl history from nhich wc '|Uotp, the upniion is advni)cr<l, 

 that " the (lesccnilinf navi,;ati(m liy ivrlificial frcshctii on ilie Lclii^li, is the 

 lirst on rccoril as a |)ertnniiiril thing." 



Thin. howoviT, is a mistalcc. for the sysltm of renricrini? shallow streams 

 n iM.:.ilj1e bv till' mudi- calleil Fliuhini^, uliicli is " to rroaiu aaarulicial (luod 

 : ■iiiir. fiy pi-nn n^; iip iIh* ii.itcr in tin- river ilM'it," aii'l then opcnmtJ the 



-v!;i ■■ "r fluud'K^tPS, when thf boats nro piissin;;. is supposed to bavp i>e<Mi 

 inventnl by tlic Kifypiian:, aflcr the t>me ol Alexander, and was found in uae 

 in il.c hyilraiilic works ut the inlrrlur uf Chum, wlii:ii '.hat cm(':rt' was vibiled 

 by the first Hnsllsli embassy. 



Sec New Edinburgh Kucyclop., Art. NaT. Inland. 



devised for joining and putting together the planks of which these 

 boats were made, and the bands became so expert that Jirt intn nould 

 putone of the xctioM togither an! launch it in forty-fire minuttn. Boats 

 of this description were used on the Lehigh till the end of the year 

 1831, when the Delaware division of the Pennsylvania Canal was par- 

 tially finished. In the last year, 40,9G(j tons were sent down, which 

 required so many boats to be built, that, if they had all been joined in 

 one length, they would have extended more than thirteen miles. These 

 boats made but one trip, and were then broken up in the city, and the 

 planks sold for lumber, the spikes, hinges, and other iron work being 

 returned to Mauch Chunk by land, a distance of eighty miles. 



" The great consumption of lunibi."r for the boats very soon made it 

 evident that the coal business could not be carried on, even on a small 

 scale, withcut a communication by water with the pine forest*, about 

 It) miles above Mauch Chunk, on the upper section of the Lehigh. 

 To obtain this was very didicult. The river in that distance had a 

 fill of about 300 feet, over a very rough, rocky bed, with shores so 

 forbidding, that in only two places above Lausanne had horses been 

 got down to the river. To improve the navigation it became 

 necessary to commence operations at the upper end, and to cart 

 all the tools and provisions by a circuitous and rough road through 

 the wilderness, and then build a boat fur each load to be sent down 

 to the place where the hands were at work, by the channels which 

 they had previously prepared. Before these channels were effected, 

 an attempt was made to send down planks singly, from the pitie 

 swamps, but they became bruised and broken by the rocks before 

 they reached Mauch Chunk. Single saw-logs were then tried, and 

 men sent down to clear them from the rocks as they became fast. But 

 it frequently happened that when they got near Mauch Chunk, a 

 sudden rise would sweep them off, and they were lost. 



" It became evident that the business on the Lehigh could not be 

 extended as f.>st as the demand for coal increased, while it was neces- 

 sary to build a new boat for each load of coal ; l)esides the forests 

 were now beginning to feel the waste of timber, (more than -lO'J acres 

 a year Ijeing cut off,) and showed ])lainly enough that they would soon 

 disappear, in consequence of the increased demand upon them. 



" Under all these circumstances, it was concluded that the time had 

 arrived for changing the navigation of tlic Lehigh into a slaekwater 

 navigation. The acting managers, who resided at MaiKh Chunk, 

 formed a plan for a steam-bout iwvigation with locks 130 feet long 

 an<l 3u feet wide, which would accommodate a steam-boat carrying 

 150 tons of coal. These locks were of a peenliar construction, adapted 

 to river navigation. The gates operated upon the same principle 

 with the sluice gates in the dams for making artificial freshets, and 

 were raised or let down by the application or removal of a hydrostatic 

 pressure below them. The fiist mile below Mauch Chunk was arranged 

 for this kind of navigation. The tocka prvred to be ftrfeetly tffcctiTt, 

 and could be filled or emptied, nolmitkatanding their magnitude, m thru 

 minutes, or about h>ilf the time of an ordinary lock." 



One of the writer's objects, in making the nbove lengthy extract, 

 was to enable the rea«ler to trace the causes which led to the abandon- 

 ment of the fl.ish navigation on the Leliigh, and to see tliat it arose 

 from no defect in the sluice g-ates or other works at first ereifted. 



It must be evident to every one that the bear Trap Htuict Uattt, 

 finding as they do their operating power in the hydrostatic pressure 

 consequent upon the difference of level which they overcome, are 

 capable of application to almost any width of opening; and that a 

 gate of lUO feet or more in length could U> manceuvreil as readily a.5 

 one of 24 feet, the only .iddition.d labour requisite being that of open- 

 ing and closing a few more wickets. 



In the descending navigation of the Udiigh, a case occurred where 

 a fall of Il"> feet in about 3t»ii w.is overcome by one of the Bear Trap 

 Sluices, though it was foui.<l necessary here to bolt a scries of b<>anis 

 upon the platfbriii, transversely across the opening, so as to mo<ierate 

 the velocity of the desceixling volume of water, by increasing it« 

 friction upon the bottom of the passage. 



N 2 



