, 1865-06-23

certainly never yet been applied to any
other cable. From first to last, indeed,
it has been subjected to a series of the
most searching electrical tests, the stand
ard of insulation being fixed at a resistance
per nautical mile equal 10 $50, 100000 of
Siemen's units, at Il temperature OF IS
degrees-a standard wholly unprecedent-
ed in any former work of the kind. In
actual practice these tests, great as they
were, have been considerably exceeded,
and the present Atlantic cable has come
out successfully from a series of trials Of
the most crucial character. The results
which have been obtained have been due
mainly TO the searching investigation IN
to the qualities Of insulating substances
which IS now practicable by means OF he
beautiful mirror gaIVan0meter OF PrOfes"
sor Thompson. Another of the tests en-
ployed was soaking separately each joint
of the gutta-percha covering for "a hours
in warm water previous 10 passing the
electric current through. A third, and
perhaps the most trying and continuous
test, wa, that of allowing no part of the
cable TO be out of the water, except while
merely IN traHSjtU from one reservoir to
the 9th r; and in conaexiou with this it
may De mentioned that the wrapping OF
iute yarn, which forms the padding,
around which the external wires are spun,
instead of being soaked in tar, as In other
cables, which has the effect of tempOrari-
ly stopping up and concealing minute
Alws, has been simply tanned to preserve
it from decay, thus admitting the water
to search out every part oil lhe cable, and
keep, in fact, constantly surrounded with
a wrapping of wet yarn.
Towards 5 O'Clock yesterday the last
few fathomS of the great coil began TO he
drawn into the machine, and in a few
minutes after the end was wound up Il
solf-acting bell rang to give notice that
the machine was empty, and almost at
the same moment the end came down in
t. the tank, and the last coil OF the cable
was slowed away. The next great Oh
jcct of interest was the inspection Of the
payi01-out apparatus, which has been al
ready fixed up, and, by means of an end
less band, kept constantly running. This
beautiful machine is an improved and cX-
tended copy, us far as general principle
is concerned, Of that used on board the
Agamemnon during the first memorable
attempts. It's improvements and modifi,
cations, however, are very great. Though
stronger and much larger, it is very much
lighter, being made almost entirely Of
wrought iron. II has six leading wheels,
round which the cable passes in deep
grooves before reaching tile main wheel
or drum, from which it will be finally sub
merged. Each groove in these six wheels
is surmounted by what is termed a jockey
pulley-that is to say, a solid wheel,
which keeps the rope down in the groove
aud prevents it overriding or getting out
Of place. The main drum is about 7ft.
diameter, and in paying out will have
three coils of cable round it, with a guild
ing piece of wrought iron pressing on
them sideways to keep them compactly
together. AS the friction on the guider
is great and constant a duplicate is pro-
yided in case of heating, which can be
put in gear with the rest Of the machine
ry without the slightest stoppage of any
part. A second drum has also been fit
ted in case of anything going wrong with
the first, Each Of these drums is fitted
with a distinct set of simple and most in
g|enious brakes, invented by Mr.. Appold