conditions, resulting from the application of electric
traction to the movement of heavy railroad trains, which had been used
initially in tunnels by the Baltimore and Ohio Railroad and was
subsequently studied and adopted by railroads in Europe, made it
possible to avoid the difficulty of ventilation connected with steam
traction in tunnels, and permitted the use of grades practically
prohibitive with the steam locomotive. The practicability of the tunnel
extension project finally adopted was thus assured.

The acquisition of the control of the Long Island Railroad by the
Pennsylvania Railroad Company, which occurred in 1900, introduced new
and important elements into the transportation problem, from a freight
as well as a passenger standpoint. Previously, the plans considered had
for their only object the establishment of a convenient terminus in New
York, to avoid the delays and difficulties involved in the necessity of
transporting passengers and freight across the North River. When the
Long Island Railroad became practically a part of the Pennsylvania
System, it was possible and desirable to extend the project so as to
provide, not only for a great prospective local traffic from all parts
of Long Island, but also for through passenger and freight traffic to
the New England States, and to and from all points on the Pennsylvania
System, thus avoiding the long ferriage from Jersey City around the
harbor to the Harlem River.

This paper has for its subject the New York Tunnel Extension project,
and is intended merely as an introduction to the detailed accounts of
the construction of the various divisions of the line to be given in
succeeding papers prepared by the engineers who actively carried out the
work. The project, however, forms the most important part of the
comprehensive scheme adopted by the Pennsylvania Railroad Company for
conducting its traffic into and through New York City, and a brief
description of this general plan is therefore necessary in order that
the relations of the tunnel line to the other parts of the
transportation project may be clearly understood.

GENERAL PLAN FOR TRAFFIC FACILITIES AT NEW YORK.

The component elements of the general plan outlined by the late A. J.
Cassatt, President, in his open letter to the Board of Rapid Transit
Railroad Commissioners of the City of New York, dated January 18th,
1906, are indicated on Fig. 1, and may be briefly summarized as follows:

_1._--The