The underground plan has many supporters in the city, these basing their hopes upon the success achieved by the underground railway of London. There are several plans proposed for an underground road. The first is known as the _Arcade Railway_. It is proposed by the friends of this plan to excavate the streets along which it passes to a depth of about twenty feet, or in other words, to make a new street twenty feet below the level of those already in existence. This new street is to be provided with sidewalks, gas-lamps, telegraph lines, hydrants, etc., and upon the sidewalks the basements of the present buildings will open, thus adding an additional and valuable story to the existing edifices. The lower street is to be arched over with solid masonry, rendered water-tight, and supported by heavy iron columns. Large glass plates, similar to those now used for lighting the cellars of stores, will be placed in the sidewalks of the street above, and will furnish light to the lower street during the day. The roadway of the lower street will be entirely devoted to the use of railway trains. The proposed route of the _Arcade_ line is from the Battery, under Broadway, to Union Square. Thence the eastern branch is to extend along Fourth avenue to the Harlem River, while the western is to continue along Broadway to the junction of Ninth avenue, whence it will be prolonged to the northern end of the island. The _Underground Railway_ proper is to extend from the lower to the upper end of the island, and is to pass through one or more tunnels, after the manner of the Underground Railway of London. The third plan for an underground road, is the only one that has yet been attempted. It is known as the "Beach Pneumatic Tunnel." A small section, several hundred yards in length, has been constructed under Broadway, and the company owning it claim that they have thus demonstrated their ability to construct and work successfully a road extending from the Battery to the upper end of the island. The tunnel is eight feet in diameter. It commences in the cellar of the marble building of Messrs. Develin & Co., at the southwest corner of Broadway and Warren street, and extends under the great thoroughfare to a point a little below Murray street. It is dry and clean, is painted white, and is lighted with gas. It passes under all the gas and water pipes and sewers. The cars are made to fit the tunnel, and are propelled by means of atmospheric pressure. A strong blast of air, thrown out by means of an immense blowing machine, is forced against the rear end of a car, and sends it along the track like a sail-boat before the wind. This current of course secures perfect ventilation within the car. The company claim that they will be able, when their road is completed, to transport more than 20,000 passengers per hour, each way. XII. HORACE GREELEY.