390 LAW AND FREEDOM IN HISTORY

been carried to the lengths attained in the event without an accompany-
ing revolution in build.

'Some increase in size would have been possible without a change in
materials. Wooden vessels could be built up to 4000, and possibly 5000,
tons, but with rapidly increasing costs of construction and maintenance.
Serious structural difficulties would have been encountered in building
very large wooden vessels, because the stems and stern-posts must needs
be single timbers, and there are fairly definite limits to the size of first-
class timbers for these purposes. The introduction of iron and steel dis-
posed effectively of all these problems. This radical change should be
borne in mind in any discussion of the size of vessels in the earlier periods.
The revolution in the character of the merchant fleet is a chapter in the
history of the late nineteenth century—an outgrowth of the development
of the iron ship.'1

The employment of iron made it feasible, as we have seen,2 to build
clippers of double the tonnage of the largest previous standard size of
sailing-ship; yet, even when the problem of construction had thus been
solved, there were limits to the possible tonnage of a sail-borne ship
even of the square rig in which the total spread of sail could be increased,
up to a point, by adding to the number of the tiers of sails and to the
number of the masts; and the size of the nineteenth-century British
merchantman, like that of the fifteenth-century Portuguese lateen-rigged
caravel,3 would have been confined, perforce, within the limits thus set
by the technique of sail-drive, if revolutionary-minded nineteenth-cen-
tury British shipwrights had not made the further innovation of pro-
pelling their new-fangled iron hulls by steam-power instead of by
wind-power. The tonnage of British steamships, as distinct from"the
tonnage of all British merchantmen, whether steam-propelled or sail-
borne, doubled between A.D. 1860 and A.D. 1868 according to Rostow;4
and the ever more preponderant part that was being played by the
increase in steam-propelled tonnage, as compared with the increase in
wind-propelled tonnage, in the aggregate increase of United Kingdom
merchant-marine tonnage, is reflected in the fact that the United King-
dom merchant marine's approximate carrying power, adjusted for steam,
rose, according to Usher,5 from 4,068,000 tons in A.D. 1850, when there
was an aggregate register tonnage of 3,651,133 tons distributed among
25,984 vessels of both kinds, to 30,924,000 tons in A.D. 1900, when there
was an aggregate register tonnage of 9,304,108 tons distributed among
19,982 vessels.6

It will be seen that, when nineteenth-century shipwrights were chal-
lenged, by the explosion of the Industrial Revolution, rapidly to cater
for an enormous increase in marine carrying capacity which had to be
conjured up somehow if an audaciously revolutionary economic enter-
prise was not to end in a catastrophic failure, the shipwrights solved the

* Usher, op. cit., pp. 477-8. z On p. 371, n. 2, above. 3 Seep, 367, above.

* See Rostow, W. W.: British Economy in the Nineteenth Century (Oxford 1948,
Clarendon Press), p. 23. s In Usher, op. cit., Table I, on p. 467.

6 In Schumpeter, J. A.: Business Cycles (New York 1939, McGraw-Hill, 2 vols.),
vol. i, p. 368, the United Kingdom merchant marine's approximate carrying-power,
adjusted for steam, is reckoned, as by Usher, at rather less than 31 million tons for
A.D. 1900, but at rather more than 8 million tons for A.D. 18*0.