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HISTORY OF ENGINEERING.

Book I.

there are then numerous locks, and a tunnel. The summit level is 978 feet above Lake Erie , and 1546 feet above high water ; the total lockage is 1063 feet.

The Ohio Canal extends from Portsmouth to Cleveland , a distance of 307 miles, and thesummit level is 499 feet above the Ohio at Portsmouth, 405 feet above the waters of Lake Erie , and 973 feet above the Atlantic Ocean . The whole district comprised by the Illinois ,Indiana , Ohio , and Michigan states, is highly favourable for the construction of canals, asthere are few natural impediments. The Ohio valley is one extensive inclined plane,watered by numerous streams ; the hills which are cut through are generally either limeor sandstone mixed with mineral coal.

The Ohio valley is divided by the river which flows in a deep ravine, and is in lengthfrom the city of Pittsburg to the Mississippi , in a straight line, 548 miles, but measured byits windings 948 miles. The height of the hills at Pittsburgh is about 1290 feet abovethe level of the sea.

The length of the Mississippi river below the point where the Ohio falls into it is 1100miles, and, allowing 3.^ inches fall per mile, we shall have 321 feet for the elevation of thespot where the junction of the two rivers takes place. The whole valley of the Ohio wasat one time a dense forest, the central plain excepted, which, as far as the sources of theMuskingum, was an open savannah covered with grass.

Lake Erie is said to be 565 feet above the surface of the Gulf of Mexico , and Pittsburgh ,which is 747 feet above the same gulf, is also 830 feet above the tide water in the Atlantic bays of Chesapeake, Delaware, Hudson, and St. Lawrence. Pittsburgh is therefore 265 feetabove Lake Erie , and distant from it in a straight line 106 miles, and it has been sup-posed, that if a channel could be cut from the Ohio at Pittsburgh to the lake, the riversAllegany and Monongahela would, instead of flowing into the gulf of Mexico , rush intothe Lake Erie , with a fall of 265 feet in 105 miles, or at the rate of feet per mile.

It is a curious fact, that the Allegany river should have its source within 5 miles of theLake Erie , and after winding from thence 200 miles should then be 265 feet above thesurface of the lake, while the Ohio does not sink in its course to the level of the lake, untilit arrives at Marietta.

At the surface of the Mississippi , immediately at the mouth of the Ohio , the level is321 feet above the Gulf of Mexico . Lake Michigan is 35 feet higher than Lake Erie , or600 feet above the level of high water in the Atlantic .

The Illinois river, which runs from the Lake Michigan , resembles in its course a windingcanal, there being only a fall of 279 feet in the distance of 520 miles, where it unites withthe Ohio , which is about 6 inches in a mile.

The valley of the Ohio , as well as that of the river Allegany, is in its inclination remarkablygentle ; from Olean, in the county of Cataraugus, to the Mississippi , a distance of 1148 miles,there are no natural impediments in the way of navigation, except those which occur at therapids of Louisville .

The Monongahela is more rapid, and the Tennessee and Kanaidha, which rise on thehigh table land of Allegany, 2000 feet above the level of the sea, are very rapid in theircourse, and impeded by many falls.

The Ohio canal has been admirably executed, and has a lockage of 1185 feet, which isovercome by 152 locks ; the width of the canal at top is 40 feet, and the depth 4 feet.

The canals in the United States are usually constructed on the principle of utility alone,little attention being paid to minutia?; their embankments are seldom dressed evenly orturfed, and timber being exceedingly abundant and easily obtained, it has been used evenfor the construction of locks; where, however, these have shown decay, stone has beensubstituted, and more finish is given in the general arrangements.

Delaware and Raritan Canal , in the state of New Jersey , is in length 42 miles; it is75 feet in width at the surface, 7 feet in depth, and has 14 locks, each 100 feet in length, by24 feet, besides a tide lock at New Brunswick ; the total lockage being 116 feet; there are17 culverts, 29 bridges, and 1 aqueduct.

This canal is supplied with water by a feeder 23 miles in length, and between 50 and60 feet in width, and 6 feet in depth. Its fall is 2 inches in a mile, and has 1 lift and2 guard locks ; there are 37 bridges, and 15 culverts.

Morris Canal, in the same state, commences at New Jersey , and is in length 101^ miles ;its ascent is 915 feet, and descent 759 feet, making a total rise and fall of 1674 feet, whichis principally overcome by inclined planes, ingeniously contrived to convey the boats fromone level to another. At each end of these is a lock, in which the boat is adjusted for itsascent, and another at the top, to elevate it to the level above; when adjusted, the whole isdrawn up by means of machinery, which serves also to lower the boats in their downwardpassage.

The elevation at Easton is 1 61 feet, and summit level 915 feet above the Atlantic .

The width of the canal is 32 feet at top, 20 feet at bottom, and 4 feet deep; the boatswhich navigate it are about 70 feet in length, and 8 feet 6 inches in breadth across thebeam; their freight is usually about 30 tons; they are drawn up the inclined planes by