THE TEHUANTEPEC SHIP RAILWAY 
71 
bottom of a dock, guided in its movements b}'’ a large niimlier of 
vertical C}dinders. The ship is then tloated in over the carriage 
and placed in exact position, the pontoon is pmni)ed out, and 
the continuous keel block comes in contact with the keel of the 
vessel, Avhen a system of hydraulic rams working through the 
deck of the caisson pushes the keel block closel}" against the keel 
and also a large number of 1 >ilge blocks and side supports against 
the side of the vessel. Each one moving up vertically comes in 
contact with the ship, Avhen the adjustable surfaces of each sup- 
port, which is faced with rubber, take the form of the vessel by 
means of a universal hinged joint. The Aveight of the vessel is 
thus uniformily distributed, according to the principle on Avhich 
the hydraulic system Avas designed. 
The locomotives are then coupled ou and the vessel hauled to 
the opposite terminal, Avhere it is set afloat by exactly the reverse 
process. At tAvo points on the isthmus it becomes necessary, in 
order to obtain grades of not more than 1 per cent and to secure 
a practically straight line, to arrange for an abrupt change of 
direction, Avhich is done by a great floating turntable, simply a 
hollow pontoon grounded on the bottom of a masonry basin 
Avhen the car is hauled upon it, and then raised slightly upon its 
bearings by pumping Avater into the basin and made to revolve 
around a vertical central axis or guide until it takes the neAV 
direction. 
There is an important advantage Avhich the ship railAvays have 
OA'er the ship canals in the American isthmus, particularly in such 
rainy portions of it as Panama and Nicaragua, the rainfall at the 
latter place ranging from 200 inches to 300 inches per annum. 
The adA'antage lies in the fact that a ship raihvay is ahvays alcove 
the floods, Avhile the canal is alAVays IacIoav them and menaced at 
all times by most serious dangers. 
The Nicaragua route has been considered the American route. 
If it is so, then the Tehuantc])ec route is still more American in 
reference to all commercial features, and certainly is of more im- 
])ortance to us from a strategic point of vicAV than any route out 
of the piril)bean. 
The cl(;ar and decided vieAA's of Admiral Shufeldt upon its ad- 
A’antages Avere exjtresscd as folloAvs: 
“ Kadi iHtliimiH rinoH into importance as it lies ncar(*r tlic center of 
American political and commercial inlluence, and the intrin.sic value of 
this eminently national work oii^dit to he hased niion the inver.«(* ratio of 
the difitance from that center. A canal throne'll the isthmn.s of Telman- 
