THE WEST SHORE.
33$
three lines, and fiimlly the ceutr.il linos suprting the
keel extend forward and aft of these vide lines nearly
the entire length of the dock. These rams are all con
neoted together by a common system of pipes fitted with
valves, by means of which they may be separated into
certain groups. When the pontoon is sunk and tho
weight of the ship is on all these rams, if tho ontire sys
tem is connected togothor, it is evident that if there be
more pressure on one ram than on another this pressure
will be equal throughout the whole system. Mr. Bads'
idea is that the ship will not be cur veil in the direction
of her length unless the roadway gives wny nudur her. A
first class roadway is therefore indispensably and this
having been provided no superior longitudinal strength
is required in the traveling oradle. But the woight has
to be distributed over the b!x rails which constitute the
track, the two outer ones of which are twenty-nine foot
opart To do this it is necessary that the traveling era
die shall be composed of Btrong transverse girders spaced
ix feet nine inches apart from centre to ooutre. If we
suppose a 8,000-ton ship upon such a cradle, having
thirty transverse girdors spaced as above under the ship's
Imttora, the problem will be to cause each one of these
girdors to carry 100 tons, or, in other words, to transfer
the excess of weight oonceutratod amidships to tho ends
of the cradle, where the vessel is lean and lucks weight
This problem is ingeniously solved iu tho following man
ner. When tho traveling cradle is run on to tho pontoon
each of the central girders comes exactly over seven of
the rams, while tho end girdors have only one rain under
them, as the keel only is to be carriod by theso girders.
By making the one ram equal in area to the aggregate
area of the seven rams under each central girder, it fol
lows that the single large ram will, with the same water
pressure, lift as much as the seven together, and that if
they all have a common pressure the one large one will
lift no more and no loss than the central seven. A few
of the girders nearer to the bow and stern have only five
rams under them, and these five have an aggregate area
only equal to that of one of the large rams. Whore the
ship becomes narrower there are ouly throe rams under
each beam, the aggregate area of the throe rams, how
ever, boing precisely equal to that of one of the single
rams at the bow or stern, where only one support is avail
able namely, under the keel. Now, if all these rams
with their diameters thus relatively adjusted I forood
up with a gentle pressure against the ship while she is
still floating, and the water valve admitting the pressure
be locked until she is lifted up by the mteon out of the
wator, it is evident that ber weight will be evenly dis
tributed throughout from stem to stern-that is, every
six feet nine inches each ram, and each series of rams,
will bold 100 tons weight
We have now got the weight of the ship evenly borne
by the pontoon, but as she has to Ims run off from this
support on her cradle on to tho railway, the next problem
is to transfor her weight from the pontoon to the crsdls
so as to obviate the nooossity of carrying the hydraulic
rami acrose the oountry undor the ship. And here an-
other simple but very ingenious arrangement comes into
operation. The heads of the rams do not come into
direct oontact with tho girders or the ship, but over every
uiu is a Voilloal nolo jiuik whiuh passu up through the
girder, and when pressure is applied by tho ram the head
of the jack is pushod up against the bottom of the ship.
Each of the largest Bixod cradles will therefore be sup
plied with a number of screw jacks equal to tho whole
mimW of rutin iu tho pontoon, tho smaller oradles hav
ing a lesser number, and when any cradle is run on to
the pontoon it is stopped and secured by a very simple
looking arrangement, so that each one of tho screws oomes
directly over a ram. The screw jack resombles nothing
so much as au orchestral music stand, for it has a flat
head, formed of steel plate, and which iu practice would
bo about three feet square. This hoad plate is soourod
ou the top of the screw by means of a toggle joint, which
enables the plate to adjust itself tit any anglo prcsouted
by the ship's side, just as tho look-rest on an invalid
chair can bo adjusted In order to proveut damage to
the ship from abrasion, the top of the plate is cushioned
with rublstr or canvas, so that it perfectly adjusts itself
to tho curvature of the vessel. Tho stem of each of these
screw jacks is provided with an adjusting nut, which is
run up against tho upcr end of the screw uear the plate
and when tho rams are down these nuts stop tho descent
of tho jack by their oonluct with tho top side of tho girder
on which they will rest Wheii the ship is floated in
over tho oradle tho heads of the screw jacks, with the nut
beneath each, are all down resting on the platform of tho
cradle, with their stems hanging below in the water,
directly over the rams. A small amount of water pressure
put upon the rams raises all these screw jacks with their
hoad plates pressed up against the bottom of the ship and
throughout the entire length of her kenL This having
been dono, the valve admitting water to the rams is
closed so that the water cannot escape, aud the pontoon
is then pumd dry and the ship raised out of the water,
supported on the screw jacks, which in their turn are
supported by the hydraulio system in the deck of the
ponkoon. In this position the nuts will be found to be at
varying heights alxive the tops of the girders. Tho nuts
are therefore screwed down with the undersides resting
on tho girders, which in effect constitute tho platform of
the cradle. The valves of the rams are now opened, and
the pressure boing relieved, the rams retire downwards
and the weight of the ship is evenly and without altera
tion transferred to the platform of the cradle.
The cradle is mounted on alxiut IUSO wheels, each
wheel being flanged on both side. Each of the platform
girders is supported by twelve strong spiral springs rest
ing on the bearings of twelve of these wheels, and as
each girder carries but 100 tons of the dead loaj, each
spring transfers to a wheel eight and a half tons. Kaoh
spring requires twenty tons to close it and has a range
of five inches. When the rams are withdrawn the weight
of the platform rest on these springs, and, of course,
partially closes them, leaving still two aud a half or three
Inches of play in each spring to allow the wheels to pass