e, and that pressure from above would
bring the whole structure down in ruins. But an opinion such
as this is due to miscomprehension of the facts. If signs of
weakening in the timbers become apparent, the remedy is very
simple. Four or more of the uprights are lined with planks,
and waste material is shot in from above, and a strong support
is at once formed, or if signs of crushing are noticed, it is
possible to go into the stope, break down ore, and at once
relieve the weight."

[Illustration: THE SQUARE SYSTEM OF TIMBERING IN MINES.]

* * * * *

TRANSIT IN LONDON, RAPID AND OTHERWISE.[1]

[Footnote 1: Abstract from a paper read before the Boston Society
of Engineers, in April, 1890.]

By JAMES A. TILDEN.

The methods of handling the travel and traffic in the city of London
form a very interesting subject for the study of the engineer. The
problem of rapid transit and transportation for a city of five
millions of inhabitants is naturally very complicated, and a very
difficult one to solve satisfactorily.

The subject may be discussed under two divisions: first, how the
suburban travel is accommodated, that is, the great mass of people who
come into the business section of the city every morning and leave at
night; second, how the strictly local traffic from one point to
another is provided for. Under the first division it will be noted in
advance that London is well provided with suburban railroad
accommodation upon through lines radiating in every direction from the
center of the city, but the terminal stations of these roads, as a
rule, do not penetrate far enough into the heart of the city to
provide for the suburban travel without some additional methods of
conveyance.

The underground railroad system is intended to relieve the traffic
upon the main thoroughfares, affording a rapid method of
transportation between the residential and business portions, and in
addition to form a communicating link between the terminals of the
roads referred to. These terminal stations are arranged in the form of
an irregular ellipse and are eleven in number.

One of the most noticeable features of the underground system in
London is that it connects these stations by means of a continuous
circuit, or "circle," as it is there called. The line connecting the
terminal stations is called the "inner circle." There is also an
extension at one end of