The New York herald., 1876-08-18

OF the passages The temucrature of the catacombs
seldom varies from hity-our degrees Fahrenheit; tho
atmosphere is damp, the floor beng generally only a
few feet above the level ofthc wells, and is al
ways precolating through the rock For the lines
underneath the streets iron tubes employed to pro-
tcct them against mechanical injury white they also
prevent the circulation OF the and retard the tecr
Grafton oi the gutta pcrcha by oxidation and by the
escape OF the essential oil, whose presence seems
necessary TO preserve its elastic condition. These
tubes are like those used for gas they OF ron
In lengths OF about eight feet, their diameter being
proportioncd TO the number wires which they have
to contain. They planted a trench a yard deep
The separate lengths are connected with lead fonts
and at distances Of from fifty l50 yards tube IS in
serted OF large diameter which sdos the ends of
two ncighboring ones, that by pushing back the
Ines can at any time bc got at for repairs These
are also used Tor drawing the cables through tubes
This Is done In lengths of 400 yards as in London the
cable beng first we'll covered with powdered tale TO
reduce the friction against the sides OF the tubes
THE BELGIAN TUBE.
Another form Of tube has been constructed in Bel
GUM The tubo is of ron, with slit three ourths of
inch broad along the upper side Tor LAYING in the
cables and saving them from the chances OF injury by
bong pulled through Whom the cables are placed In
tho tube length OF iron, broader the top nangc
than the siit Is put INTO each length fastened there
by means OF three iron wedges passing through holes
In the upper rib OF the ron The space above the
nangc TO the hcgh, OF the top OF the tube then filed
In with waertight cement, which seals up com
pctey, put which can at any time be removed with a
chise IN order that the cables may be lifted out
paired VI necessary The Jont between two lengths ot
tube IS made ny ribbed clip which presses collar of
vuicanizcd rubber two slightly elevated on
the neghborng ends OF the tubes At regular inter-
walls tho tubes enter testing boxes formed by
cylindrical chambers covered with fat lids packed with
iudlnrubbcr rings
"A new method Of constructing underground lines
has been recently tried In Holland. The tubes arc
made OF creosotcd wool and wircs after being In
sniacd with gutta pcrcha placed IN the tubes and
tue space hled with resduum OF tho disIlalion of
coal tar. v
DIFFICULTIES OF OPERATING UNDERGROUND LINES
In regard 20 the difficulties to bc overcome in practi-
cahy working Underground lines. and the chances
alter construction OF their proving an utter failure Mr.
Prescott gives the following Interesting statement:
ASIDE from the dI,cutcs incident to tho insulation
oil Underground lines there stlll another difficulty OF
cqua. u not greater, magnitude TO be encountered.
which Is due to the effects ot static induction These
effects were hrst observed upon the subtrranean
wh'ch we're constructed in Prussia Ia lS4S When the
lines were under construction between Berlin and
Frankfort, on the Nam, and Cologne in ls4s the cleo
trcians were astonshed TO observe that, while they
were able to speak with the great, 81 case
land line from Berlin to Magdcburg scventysix miles
they found 1t absolutely impossible to do SO un
derrround line OF the same length They at FIRST at
triouicd the difficulty to imperfect insulation, but u
soon appeared that the better insulation the greater
bccsmc the difficulty, and the insulation was actually
discharged In order TO enable them to communicate
Those dioicuss were soon justly attributed 10 tn,