WHY DO LAWS OF NATURE NOT ALWAYS WORK? 389
By contrast, from circa a.d. 1830 onwards, increases in the size of
ships, requiring revolutionary changes in their build, and soon also in
their drive, came to contribute far more than increases in the number
of ships in commission towards the now steeply rising increase in the
aggregate tonnage of the United Kingdom merchant marine, as can be
seen from the following figures in the tables compiled by Usher,1

Year	Number of vessels	Register tonnage	
1788
1830
1860
1890
1910	12,461
19,174
27,663
21,591
21,090	1,279,063
2,201,592
4,658,687
7>978,53S
11,555,663	
Percentage of Vessels in the United Kingdom Merchant Marine in Each of
the Different Tonnage-Classes Distinguished in the Series of Columns Set
Out Below

Year	Under 100 tons	100-419 tons	420-1,199 tons	
1788
1830	31-1
25-2	62-1
62-4	6-8
12*4	

Year	Under zoo
tons	100-399
tons	400-1,199
tons	r,5oo-j,999
tons	2,000-3,999
tons	4,000 tons
and over	
1869	9-6	27-4	45-9	15-6	1-2	0-3	
It is manifest that the almost six-fold increase in the United Kingdom
merchant marine's aggregate register tonnage from a figure of 1,551,072
tons in a.d. 1799 to a figure of 9,304,108 tons in a.d. 1900 was mostly
accounted for by an increase in the size of vessels, and not by an increase
in their numbers, considering that, between the same two dates, that
saw a 600 per cent, increase in aggregate tonnage, the numbers increased
by hardly more than 50 per cent., from 12,461 in ajd. 1799 to 19,982 in
ajd. 1900, after having reached and passed in aj>. 1860 a peak figure of
27,663.2 It is no less evident that the increase in size could never have
cit., p. 474). 'The rapid growth in the seventeenth century is comparable to the growth
of the late nineteenth century, which we have been inclined to think of as unexampled
in the centuries preceding* (ibid., p. 472). Yet, in spite of the building of sixteen ab-
normally large East Indiamen during the years A.D. 1675-80, an increase in size evidently
counted for much less than an increase in numbers in the doubling, between a.b. 1663
and 1688, of both the tonnage of the English merchant marine and the clearances in
England's foreign trade (see the figures in Table I, on p. 467, and Table II, on p. 469,
of Usher, op. cit.). 'It is important to note that the commercial growth of the late seven-
teenth century, as shown by both sets of data, was not accompanied by any large increase
in population, whereas the increase hi population was very considerable in the nineteenth
century* (ibid., p. 474).
 1	The two sets of figures set out above are extracted respectively from Table I, on
p. 467, and from Table IV, on p. 475, of Usher, op. cit. In Table I the figures for
a.d. 1830, by comparison with those for a.d. 1788-1825, have been cut down by about
7 per cent, through the exclusion of lost vessels formerly carried on the register. The
figures of.tonnage for the years beginning with a.d. 1860, by comparison with those for
aj>. 1830—50, have been raised by about 7-5 per cent, through a change in the rules for
the measurement of tonnage that became effective in a.d. 1857.
 2	See Usher, op. cit., Table I, on p. 467.