ates went the Cumberland National Road to the Ohio。 New York instantly； in her zone； took up the challenge and thrust her great Erie Canal across to the Great Lakes。 In rapid succession； Pennsylvania and Maryland and Virginia； eager not to be outdone in winning the struggle for Western trade； sent their canals into the Alleghanies toward the Ohio。
It soon developed； however； that Baltimore； both powerful and ambitious； was seriously handicapped。 In order to retain her commanding position as the metropolis of Western trade she was compelled to resort to a new and untried method of transportation which marks an era in American history。
It seems plain that the Southern rivals of New York City Philadelphia； Baltimore； and Alexandriahad relied for a while on the deterring effect of a host of critics who warned all men that a canal of such proportions as the Erie was not practicable； that no State could bear the financial drain which its construction would involve； that theories which had proved practical on a small scale would fail in so large an undertaking； that the canal would be clogged by floods or frozen up for half of each year； and that commerce would ignore artificial courses and cling to natural channels。 But the answer of the Empire State to her rivals was the homely but triumphant cry 〃Low Bridge！〃 the warning to passengers on the decks of canal boats as they approached the numerous bridges which spanned the route。 When this cry passed into a byword it afforded positive proof that the Erie Canal traffic was firmly established。 The words rang in the counting…houses of Philadelphia and out and along the Lancaster and the Philadelphia…Pittsburgh turnpikes〃Low Bridge！ Low Bridge！〃 Pennsylvania had granted； it has been pointed out； that her Southern neighbors might have their share of the Ohio Valley trade but maintained that the splendid commerce of the Great Lakes was her own peculiar heritage。 Men of Baltimore who had dominated the energetic policy of stone…road building in their State heard this alarming challenge from the North。 The echo ran 〃Low Bridge！〃 in the poor decaying locks of the Potomac Company where； according to the committee once appointed to examine that enterprise； flood…tides 〃gave the only navigation that was enjoyed。〃 Were their efforts to keep the Chesapeake metropolis in the lead to be set at naught？
There could be but one answer to the challenge； and that was to rival canal with canal。 These more southerly States； confronted by the towering ranges of the Alleghanies to the westward； showed a courage which was superb； although； as time proved in the case of Maryland； they might well have taken more counsel of their fears。 Pennsylvania acted swiftly。 Though its western waterway the roaring Juniata； which entered the Susquehanna near Harrisburghad a drop from head to mouth greater than that of the entire New York canal； and； though the mountains of the Altoona region loomed straight up nearly three thousand feet； Pennsylvania overcame the lowlands by main strength and the mountain peaks by strategy and was sending canal boats from Philadelphia to Pittsburgh within nine years of the completion of the Erie Canal。
The eastern division of the Pennsylvania Canal； known as the Union Canal； from Reading on the Schuylkill to Middletown on the Susquehanna； was completed in 1827。 The Juniata section was then driven on up to Hollidaysburg。 Beyond the mountain barrier； the Conemaugh； the Kiskiminitas； and the Allegheny were followed to Pittsburgh。 But the greatest feat in the whole enterprise was the conquest of the mountain section； from Hollidaysburg to Johnstown。 This was accomplished by the building of five inclined planes on each slope； each plane averaging about 2300 feet in length and 200 feet in height。 Up or down these slopes and along the intermediate level sections cars and giant cradles （built to be lowered into locks where they could take an entire canal boat as a load） were to be hauled or lowered by horsepower； and later； by steam。 After the plans had been drawn up by Sylvester Welch and Moncure Robinson； the Pennsylvania Legislature authorized the work in 1831； and traffic over this aerial route was begun in March； 1834。 In autumn of that year； the stanch boat Hit or Miss； from the Lackawanna country； owned by Jesse Crisman and captained by Major Williams； made the journey across the whole length of the canal。 It rested for a night on the Alleghany summit 〃like Noah's Ark on Ararat；〃 wrote Sherman Day； 〃descended the next morning into the Valley of the Mississippi； and sailed for St。 Louis。〃
Well did Robert Stephenson； the famous English engineer； say that； in boldness of design and difficulty of execution； this Pennsylvania scheme of mastering the Alleghanies could be compared with no modern triumph short of the feats performed at the Simplon Pass and Mont Cenis。 Before long this line of communication became a very popular thoroughfare； even Charles Dickens 〃heartily enjoyed〃 itin retrospectand left interesting impressions of his journey over it：
〃Even the running up； bare…necked； at five o'clock in the morning from the tainted cabin to the dirty deck； scooping up the icy water； plunging one's head into it； and drawing it out； all fresh and glowing with the cold； was a good thing。 The fast； brisk walk upon the towing…path； between that time and breakfast； when every vein and artery seemed to tingle with health； the exquisite beauty of the opening day； when light came gleaming off from everything； the lazy motion of the boat； when one lay idly on the deck； looking through； rather than at； the deep blue sky； the gliding on； at night； so noiselessly； past frowning hills； sullen with dark trees； and sometimes angry in one red burning spot high up； where unseen men lay crouching round a fire； the shining out of the bright stars； undisturbed by noise of wheels or steam； or any other sound than the liquid rippling of the water as the boat went on； all these were pure delights。〃*
* 〃American Notes〃 （Gadshill Edition）； pp。 180…181。
Dickens also thus graphically depicts the unique experience of being carried over the mountain peaks on the aerial railway：
〃There are ten inclined planes； five ascending and five descending； the carriages are dragged up the former； and let slowly down the latter； by means of stationary engines； the comparatively level spaces between being traversed； sometimes by horse； and sometimes by engine power； as the case demands。 Occasionally the rails are laid upon the extreme verge of a giddy precipice； and looking from the carriage window； the traveler gazes sheer down； without a stone or scrap of fence between； into the mountain depths below。 The journey is very carefully made； however； only two carriages traveling together； and while proper precautions are taken； is not to be dreaded for its dangers。
〃It was very pretty traveling thus； at a rapid pace along the heights of the mountain in a keen wind； to look down into a valley full of light and softness； catching glimpses； through the tree…tops； of scattered cabins； children running to the doors； dogs bursting out to bark； whom we could see without hearing； terrified pigs scampering homewards； families sitting out in their rude gardens； cows gazing upward with a stupid indifference； men in their shirt…sleeves looking on at their unfinished houses； planning out tomorrow's work； and we riding onward； high abode them； like a whirl…wind。 It was amusing； too； when we had dined； and rattled down a steep pass； having no other motive power than the weight of the carriages themselves； to see the engine released； long after us； come buzzing down alone； like a great insect； its back of green and gold so shining in the sun； that if it had spread a pair of wings and soared away； no one would have had occasion； as I fancied； for the least surprise。 But it stopped short of us in a very business…like manner when we reached the canal； and； before we left the wharf； went panting up this hill again； with the passengers who had waited our arrival for the means of traversing the road by which we had come。〃*
* Op。 cit。
This Pennsylvania route was likewise famous because it included the first tunnel in America； but with the advance of years； tunnel； planes； and canal were supplanted by what was to become in time the Pennsylvania Railroad； the pride of the State and one of the great highways of the nation。
In the year before Pennsylvania investigated her western water route； a joint bill was introduced into the legislatures of the Potomac Valley States； proposing a Potomac Canal Company which should construct a Chesapeake and Ohio canal at the expense of Maryland； Virginia； and the District of Columbia。 The plan was of vital moment to Alexandria and Georgetown on the Potomac； but unless a lateral canal could be built to Baltimore； that city which paid a third of Maryland's taxeswould be called on to supply a great sum to benefit only her chief rivals。 The bitter struggle which now developed is one of the most significant in commercial history because of its sequel。
The conditions underlying this rivalry must not be lost sight of。 Baltimore had done more than any other Eastern city to ally herself with the West and to obtain its trade。 She had instinctively responded to every move made by her rivals in the great game。 If Pennsylvania promoted a Lancaster Turnpike； Baltimore threw out her superb Baltimore…Reisterstown boulevard； though her northern road to Philadelphia remained the slough that Brissot and Baily had found it。 If New York projected an Erie Canal； Baltimore successfully championed the building of a Cumberland Road by a governmental godmother。 So thoroughly and quickly； indeed； did she link her system of stone roads to that great artery； that even today many well…informed writers seem to be under the impression that the Cumberland Road ran from the Ohio to Washington and Baltimore。 Now； with canals building to the north of her and canals to the south of her； what of her prestige and future？
For the moment Baltimore compromised by agreeing to a Chesapeake and Ohio canal which； by a lateral branch； should still lead to her market square。 Her scheme embraced a vision of conquest regal in its sweep； beyond that of an