A correspondent of the New York Tribune, vriting from Philadelphia, asserts that the Pennsylvania Central Railroad, which is 345 niles long, only cost about one-half as much IS the New York and Erie Railroad; the lat;er, however, is 100 miles longer. Its returns, t seems, are nearly as large as the Erie, there'ore it must be in a prosperous condition. Its ncome from January 1st, 1858, until April Lst, was $1,717,449 ; that of the Erie luring the same time, $1,719,211 ; and the Baltimore and Ohio line, (386 miles long,) ^1,327,752. It is stated that about one hunIred emigrants, in search of farms, go over he P. C. R. R. daily ; the cars provided for ;hem are of a superior character to those beonging to emigrant trains on other railroads.