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32 partly destroyed by dynamite, the bank at the abutment having given. way. It has since been rebuilt, and together with dam 2 was placed in commission in October last. These improvements extend navigation toe Natrona, in former years better known as the "Soda Works." Briefly these constitute the govern- THE MARINE REVIEW stream 000 to 2,500,000 tons. The traverses a splendid valley, exceeding- ly well adapted for manufacturing purposes. Its mineral resources are large and diversified, comprising coal, building stone, fire clay, limestone, glass sand, iron ore, ete. The pres- ent slackwater system does not reach these except a small portion of the STRUCTURAL STEEL FRAME WORK FOR LOWER GATES IN OHIO RIVER MOVABLE / STEEL BEAR TRAP GATE AT. HERR ISLAND DAM, ALLEGHENY RIVER SHOWING FREE END OF LOWER LEAF, HINGE PEDESTALS OF UPPER LEAF, PIER UNDERCUT, ETC. ment's navigation improvements on the two streams forming the Ohio river at Pittsburg. While the Monon- gahela, with its 130 miles of perma- nently navigable waters, can boast of a 12-000,000-ton annual cOmmerce the Allegheny must not be rated as an insignificant stream because at the beginning of its radical navigation career it can show only an annual commercial movement of from 2,000,- LEAR OP BEAR TRAP DAM. portant feeders. For fully thre. quarters of a century Operations on the Ohio were confined Principally to the removal of rock and *snag ob. structions, the dredging of channels . and bars and the construction of de. flecting dikes and low dams closing duplicate chutes at heads of islands and, bars: Barly in the 70's" gaa. 5 feo ede 9 Pa writin sa A Lee BE Engin eer Offs aes ty me isa STEEL FRAMEWORK OF OHIO RIVER ROLLING LOCK GATE (IN GATE RECESS). coal, but an: additional three' dams would readily extend navigation into the heart of the mineral region. No funds have yet been made available for the. extension of a_ slackwater above dam 3. But' the improvement. of greatest moment in this region is that per- taining to the Ohio river, to which the Allegheny and Monongahela _ are related rather in the nature of itis » BEAR TRAP GATE 'IN HERR ISLAND DAM NO 1 ALLEGHENY RIVER, SHOWING STEEL LOWER LEAF NEARLY COMPLETED. was set on foot movable dam _ at order to establish a seasons of low water at Pittsburg, and incidentally to accom- plish the initial step toward the per- manent improvement of the stream. In 1878 construction work was com- menced, but under the prevailing sys- tem of intermittent was greatly delayed, finally resulting GV oa to movement CONSTIUCT: a Davis island in in harbor appropriations ents