POLK, LEOXIDAS. 



679 



tubo, glides smoothly along toward its < 

 nation, the revolving disc keeping up the motive 

 power until it reaches the steep incline, whence 

 its own momentum again suffices to carry it the 

 rest of the distance. The return journ< 

 above indicated, is effected by the aid of the 

 exhausting process. At a given signal a valve 

 is opened, and the disc-wheel set to work in 

 withdrawing the air from the tube. JSTear the 

 upper end of the tube there is a large aperture, 

 or side-vault, which forms the throat through 

 which the air is, so to speak, exhaled, the iron 

 doors at the upper terminus still being kept 

 shut. In a second or two the train posted at 

 the lower terminus, yielding to the exhausting 

 process going on in its front, and urged by the 

 ordinary pressure of the atmosphere from be- 

 hind, moves off on its upward journey, and 

 rapidly ascending the incline, approaches the 

 iron gates, which fly open to receive it, and 

 it emerges at once into daylight. Such is the 

 mode in which the system works, and it seems 

 capable of being adapted to railway communi- 

 cation within the metropolis and other large 

 towns, or wherever tunnelled lines with steep 

 gradients exist. The chief obstacles encounter- 

 ed in practically working the atmospheric rail- 

 way, introduced some fifteen years ago, are 

 considered to have been effectually overcome 

 by the present modification of the principle. 

 Under the former system the tube was of very 

 small size, and fixed upon the ground ; a longi- 

 tudinal or continuous valve opening at the top, 

 along which a rod, connecting the piston with 

 the carriages, passed, and the valve closing be- 

 hind the road as it moved onward. The amount 

 of atmospheric pressure required to be exerted 

 where the area of the tube was so small, was en- 

 ormous, being from seven pounds to ten pounds 

 per square inch ; whereas upon Mr. Rammell's 

 principle the pressure is only two and a half 

 ounces per square inch, and, moreover, the great 

 leakage and waste of power which rendered the 

 old atmospheric system so costly in working are 

 here in a great measure avoided. It need hard- 

 ly be added that the worst drawbacks to travel- 

 ling through tunnels viz., the smoke and sul- 

 phurous vapors emitted from the locomotive, 

 and the close, unwholesome atmosphere of the 

 tunnels themselves are in this case got rid of. 

 Every tram, in fact, carries its own supply of 

 fresh air along with it, and also expels the foul 

 air before it. 



POLK, LEOXIDAS, a bishop of the Protestant 

 Episcopal Church, and General in the Confed- 

 erate service, born in Raleigh, X. C., in 1800, 

 died near Marietta, Ga., June 14, 1804. He 

 was graduated at Yv'est Point iu 1827, and ap- 

 pointed a brevet second .lieutenant of artillery ; 

 but having, through the influence of Bishop 

 Mcllvaine, then chaplain at West Point, been 

 induced to study for the ministry, he resigned 

 his commission in December, 1827, and three 

 years later was ordained a deacon in the Prot- 

 estant Episcopal Church. From 1831 to 1838 

 he officiated at various places in the South, and 



in the latter year he was consecrated Missionary 

 Bi-hop of Arkansas and the Indian territory 

 south of 36 30', with provisional charge of the 

 dioceses of Alabama, Mississippi, and Louisiana, 

 and the missions in the republic of Texas. In 

 1841 he resigned these charges, with the ex- 

 ception of the diocese of Louisiana, of which he 

 remained bishop until the close of his life. The 

 outbreak of the rebellion found him a strong 

 sympathizer with the doctrine of secession. 

 His education and associations were strongly 

 southern, and his property, which was very 

 considerable in lands and slaves, helped to 

 identify him with the project for establishing 

 a Southern confederacy. His familiarity with 

 the Valley of the Mississippi prompted him to 

 urge upon Jefferson Davis and the rebel author- 

 ities the importance of fortifying and holding 

 it.? strategical points, and amidst the excitement 

 of the time the influence of his old military 

 training became uppermost in his mind. L'n- 

 der these circumstances the offer of a major- 

 generalship by Davis was regarded not unfavor- 

 ably, in spite of the sacred calling which he had 

 followed during thirty years. He applied to 

 Bishop Meade, of Virginia, for advice, who 

 declined to give it, but referred him to Gen. 

 Robert E. Lee, as one to whose judgment he 

 might safely defer. Lee unhesitatingly advised 

 him to accept the commission, and he at once 

 did so. His first command extended from the 

 mouth of the Arkansas River, on both sides of 

 the Mississippi, to Paducah, on the Ohio, his 

 headquarters being at Memphis ; and his first 

 general order, issued July 13th, declared that 

 the invasion of the South by the Federal 

 armies " comes bringing with it a contempt 

 for constitutional liberty, and the withering 

 influence of the infidelity of Xew England and 

 Germany combined." It was under his gen- 

 eral direction that the extensive works at Forts 

 Donel^on and Henry, Columbus, Ky., Island 

 Xo. Ten, Memphis, and other points were con- 

 structed, and the skill with which they were 

 selected for defence testifies to his thorough 

 military training. He held this command until 

 the spring of 1862, when, in consequence of the 

 signal Federal successes in that part of the 

 country, he was relieved and ordered to join 

 Johnston's and Beauregard's army at Corinth. 

 As commander of a corps he participated in the 

 battle of Shiloh, and in the subsequent opera- 

 tions ending with the evacuation of Corinth. 

 He afterwards held a command in the army of 

 Gen. Bragg, took part in the battle of Perry- 

 ville during the invasion of Kentucky in the 

 autumn of 1862, and saw much hard fighting 

 at the stubbornly contested battle of Murfrees- 

 boro. Still serving under Bragg, he fell back 

 with him beyond Chattanooga before the steady 

 advance of Gen. Rosecrans in the campaign of 

 1863, and had a share in the victory of Chicka- 

 mauga. For disobedience of orders in this bat- 

 tle, whereby, as was asserted by Gen. Bragg 

 in his official report, the Federal army w-a* 

 alone saved from annihilation, he was relievec 



