The new (jovemment irostal Service between New York and Chicago, whicU contemplates two fast mail traius between those poiats, which has been posted to open ou the 16th inst., has, it seems, met a delay. Postniaster-General Jewell states trom 'Washington, that it will not begin before the 18th, and possibly not until a week later. Mr. Bangs has completed all the minor details, and has tixed upon the 16th oï September next as the day upon which the primal trip shall be made. Two traius leave on that day siinultaneously froru Chicago and New York. That leaving Chicago will start at 8 o'clock ou the evening of the 16th, while the westward bouud train will leave New York at 4:15 o'clock ou the morning of the 16th. The train froin Chicago will reach Cleveland at 7 oclock the following morning, Dunkirk at uoon of the same day, Buffalo at 1:25 P. M., Syracuse at 5:20 P. M., Albany at 9 P. M., and New Yoik City about niidnight of the 17th. The train from New York will leave, as has been stated, at 4:15 A. M., reaching Albany at 7:55 A. M., Symcuse at 11:25 A. il., Buffalo at 3 v. M., Cleveland at 8 P. M., Toledo at 11 P. M., and Chicago at 6:30 A. M. of the 17th. Pretty quick tirue, beiug only 26 houra between New York and Chicago. No stops will be made except for the purpose of changing engines. These traius will be composed of au engine and tender and tour postal cars or more, if the present or growing demands of the service require it. The first train will convey inembera of the press of Chicago and New York. Goiug eastward no way mails will be supplied betweeu Chicago aud Toledo, and westward from New York, no way service will be doue between that city and Albany, as the present services on both extremes of the route is ampie to supply all demanda. Way muil service, which, in less tecunical vernacular, means " supply all stations on the line,' will be performed, on the eastward and westward trips between Toledo and Albany. And here will the value of Mr. L. F. Ward's mailcatchers be practically demonstrated. For the trains will uot slack up at eveu the large towns, except at those already named, to exohauge mails. These catchers consist of an arm attached to each Postal car, by whioh the mail-bag, arrauged on an upright beam at the side of the track, is caught while passing through without placing in jeopardy the lives of the Postal clerks, so long as they are reasonably careful. All overlaud mails will b carried on this fast train, aud it is estimated by Captain White tbat the aggregtite daily weight of mail matter conveyed eastwtird and westward will be about 20 tons.