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JOURNAL OF THE PLYMOUTH INSTITUTION. 
end, and huge flood-gates are required to regulate the tides, and 
prevent too swift a current in the waterway. So there is no fear 
of the Gulf Stream being diverted ; and, further, the mean level 
of the tides on both sides the Isthmus is about the same. 
In passing it may be as well to state that two rival schemes are 
projected. First a canal further west in the isthmus by way of the 
San Juan River and Lake Nicaragua. This route is 180 miles 
long ; but in consequence of making use of the river and lake it 
will not cost a quarter as much as M. de Lesseps' canal. But it is 
still in nubibus, and would be a bad speculation in competition 
with the other shorter and therefore better means of communication. 
The other rival scheme is a ship railway in Mexico, from the 
Gulf of Mexico to the Pacific, to cost £15,000,000. The ship is 
to be lifted by pontoons on to a trolly, on twelve lines of rail, and 
drawn by six steam-engines, each capable of drawing 2,000 tons, a 
distance of 134 miles by land, from sea to sea. Cradles are to be 
provided, of different sizes for different ships, to prevent straining. 
Before treating of the effect the Suez Canal has had, and the 
Panama Canal will have, upon the trade and commerce of the 
' world, including England, and of the effect the Canadian-Pacific 
Railway will have upon England and ourselves locally, and how 
other and older and present routes are and will be influenced 
thereby, it will be useful for a few minutes to describe the rapid 
strides that have been made in the means of crossing the ocean, 
by improvements in the speed and capacity of steamers. 
In 1838 the Great Western steamship crossed the Atlantic, 
and in 1840 the Britannia, the first Cunard steamer; and the 
Company, with that and other ships, kept up the mail service at a 
speed of eight and a half knots an hour. These were paddle 
boats. In 1850 iron boats propelled by screws came into use, and 
gradually the size of the vessels increased until we have now a 
ship of 8500 tons instead of 1156 tons, and of 542 feet in length 
instead of 207 feet, with a speed of over twenty knots an hour 
instead of eight and a half. And engineers state that express 
steamers can be built, carrying only passengers and no cargo, with 
twin screws, to run forty miles an hour. 
Having thus described the various engineering works, forming 
or to form different means of communication between various 
