DOCUMENTARY HISTORY OF THE FLORIDA CANAL 11

cargo tons or simply tons. Again, for cargo purposes we find the "measurement
ton" of 40 cubic feet for commodities that bulk large per unit of weight. In
fact, we find no less than 13 different units of weight and/or measure, all called
"tons." For the purposes of our report we preferably use the short ton of 2,000
pounds for commerce or cargo, but for navigation or shipping we have adopted
the dead-weight ton, which is the carrying capacity of a ship in tons of 2,240
pounds.
 A vessel may or may not be loaded to capacity, but in any event that dead-
weight tonnage capacity represents capital invetment-just as a freight car or
a motor truck, whether loaded or empty, represents capital. Again, it is this
dead-weight capacity that must be moved, requiring crew, fuel, subsistence, and
ship supplies, and enters into the operating costs-although often in an inverse
ratio. That is to say, the lager.t ship the lower the. costs per revenueton.
This inverse ratio explains thd-steady trend toward larger slips and this trend
must be considered in designing or improving any waterway or harbor project.
 Before leaving this point we would say that the "displacement tonnage" or
actual weight of the ships would possibly have given us a better measure of capital
invested and the daily operating costs, but it was not conveniently available.
There is, moreover, no fixed relation between the various kinds of ship tonnage.
The large de luxe passenger steamers have a high displacement tonnage but since
they have but little cargo space they have a low dead-weight tonnage. Oil
tankers and ore carriers, on the other hand, may and do have a high displacement
tonnage and a high dead-weight tonnage as well as a high gross and net registered
tonnage.
 11. Pr~ent Gulf commerce or cargoes.-Available statistics present this com-
merce under two general headings, namely, foreign traffic and domestic traffic.
The former is again subdivided two ways into imports and exports-or traffic
in-bound and out-bound, respectively. Domestic traffic i subdivided three ways
as coastwise receipts (in-bound) and coastwise shipments (out-bound), and
another group classified as "Other domestic." Therefore, to eliminate duplica-
tions and to determine what part of the commerce might profit by the proposed
waterway, we have supplemented Government statistic by the private records
of shipping companies, and by dint of much arduous effort in assembling, com-
piling, analyzing and finally synthesizing we have arrived at figures which we
believe to be complete and accurate.
 For basic purposes we have usqd the statistics for the year 1929 as the latest
year for which complete figures are available. Our studies disclose a grand total
of cargoes loaded and discharged in all the Gulf ports amounting to 83,115,433
short tons. Of this amount, 31,712,335 tons, valued at $821,155,134, were
transported as domestic commerce between ports on the Atlantic coast of the
United States and all Gulf ports except those in Mexico. In the foreign trade
13,462,371 tons, valued at $798,233,872, moved between the United States Gulf
ports and the foreign ports embraced in those parts of Canada, Europe, and Africa,
most directly served by the proposed canal.
 12. For convenience that foreign trade region on both sides of the Atlantic is
designated in tlis report as "Area A". It includes all ports of Atlantic Canada
and Newfoundland, of North Atlanti and Baltic Europe, of the Havre-Hamburg
Range in Europe, of South Atlantic Europe, of the. West Mediterranean, and of
the East Mediterranean and the Black Sea. It includes ports in northern Africa
and some ports beyond the Sues Canal.
 13. The minimum total cargo in United States trade for 1929 to be benefited
by the canal amounted to 45,174,704 short tons, valued at $1,619,388,906.
These figures are under the actuality, for it was not practicable to contact all
shipping companies engaged in coastwise trade and few of those actually con-
tacted were able to supply complete data on in-bound shipments, which consist
largely of package freight. Data are more easily had on out-bound freights, for
these consist largely of commodities in bulk, as, for example, cotton, petroleum,
grain, and flour. Statistics are not available for Mexican ports, but not less than
1,500,000 tons of petroleum would have benefited by the short route. Other
Mexican tonnage would undoubtedly also have profited, and the grand aggregate
in round numbers would have been not less than 47,000,000 short tons.
 14. Potenial commerce.-In that division of this report relating to commodity
studies will-be found*- discussion of-probable future commerce for the 16-year
interval ending with 1945. Independently of that discussion, but as a rough
check thereon, the trade of the Gulf as a whole has been reviewed for the past
10 years. The results are set out in detail in that section (exhibit 349) entitled
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