TRANSACTIONS OF THE 8ECTIONS. 
155 
an ocean wave on a vessel of such extraordinary length. 1 1 is true that such n ' ‘ ‘ * 
may often cross the Atlantic without encountering such a sea as would endangf i h r. 
Henderson affirms that he has seen waves of a height of 50 feet, Rom crest 
to hollow, and argues that it is impossible fora vessel of this length and proportion t 
U lipt under command in snch u sea should any accident happen to her mac uner\. 
Toe investigations of Dr. Scoresby show that the elevation of the Atlantic waves 
hard gale was as much as 43 feet. Others estimate the mean elevation nt 
»f«t, with a length of lfio feet, and a velocity of 30 miles per hour. W c may tlicrc- 
estimate the usual gales in the Atlantic as producing u wave 25 feet in height 
«d!00 feet long. The author doubts the capacity of such a ship under such pres- 
•ures, and cites examples of this in three American steamers, the ' Pro me, the 
Vanderbilt/ and the ‘ San Francisco.’ The former was lost; the Vanderbilt fell 
'nil \hc trough of the sea, and was struck by a wave which carried away all her 
Wwarka, made a clean sweep of her deck-houses, and put out all her fires. The 
', :u Francisco, a large steamer, bound to California, caught in a north-west gale in 
w Gulf-stream, being disabled got into the trough of the sea; she became per- 
unmanageable, and part of the crew and 150 passengers were washed off her, 
I decks actually being stave in, they having no command over her when under sail 
5 «dq. This difficulty may be obviated by the ship being provided with a rudder nt 
«em as well as the stern, and by having before the after rudder, and above the 
f rew shaft, a steering puddle or three-armed paddle across the stern, the wheel being 
•wo-thirds its diameter above water, to be worked by a ten-horse engine. 
DfiRcrtptive ftfcaaurmvnt for 'Tonnage. 
j ft R “ Act passed in 1830, aud amended in 1845. a rule was adopted, based on the 
diviy v '“““rcwwrtof eleven breadths and four depths, taken at three sections, the 
In iRin°i eav 1 il ' s tbe registered tonnage. 
Antr l “ e tonnage Committee, including Mr. Parsons and Mr. Moorsom, ship- 
f) rdBrtTk ^ mercantile captains, reported “that the equitable basis charges 
tD «aand , ®“ t ’ 1,arbour » and other dues, was that of the entire cubical contents 
inj cu !; eternally to the height of the upper deck by the use of diagrams of sections 
MI M ot ar< -'U8.’’ 
<&£**** P r °P oaed n, mode of computing the internal capacity without the aid 
n Wore p' 8 ° r ? uives °f ureas, aud of ascertaining the tonnage by dividing by 100 
termed | 1ttvenieu t. In May 1850, the author transmitted to the Board of Trade a 
'"lit mj p ' an ; showing that the mode of external measurement and computing the 
ca picit v . i‘ n , tllc bl11 of 1850, is equally applicable to ascertaining the internal 
>*Uy aj ’ “ Ul1 tbat by one measurement, taken either externally as in bill, or inter- 
[n P H k ' )y Mr ’ Moorsom, both the external bulk and internal space could 
To meet tk • meaas ol ~ transverse sections and curves of areas. 
^wr-buii* y lnet l Ufl ,'itiea of light, goods and dead-weight cargoes, and those of 
L n - ‘he Rdv 'f a aTul ,rou vessels, it was then proposed, ami still advocated, to com- 
of 18 '()^ eternal measurement, recommended by the Tonnage Com- 
^opted itiAnrilT^- P 1 ® iat f rna ^ measurement proposed by Mr. Moorsom and 
r ' f the eitwiml Iu’ ,u tbe b*U to come into operation in 1855, by taking the mean 
b9t Ween tiiut.pfL. aiul internal space in cubic feet, thus forming an average 
tonaacc *2^ iron B ^‘P 9 * belli curgu and dead weight, as tlic basis of 
^vrrifti bulk ,, ’ 7. * " in age Committee in 1840 ascertained, by measuring the 
to the^'lb C0 . uteHta of many vessels, that the ratio of old, or builder’s, 
'^adopted ,i U , ?. r displacement tu upper deck was 27 - 100 ths. The factor - 27 
. b,U 15S* b ! U ot ' 
^nuag 0 baaed on . pta 100 ni the divisor of the internal capacity for the register 
to- 6 * f'»r external _ e Iul °rnal space only, instead of which it is proposed that the 
jj'i’ftibg Bin boforp a > UretUen ^ should be Oilded to the 20 th clause of the Merchant 
Ilrn r? thfi °f the rn. T'h 8 iato °P cr *tion in May 1855. A factor of 30, 31, or 
in Produce a r m/ U * JU * an ^ 8 P ace could he fixed for each 500 tons, so that it 
f.* thus armr^!* cr ^unnage a little below the old law or builder’s measure- 
eitl IC P ra ctieabilit v „f l I^ ate tbc ru * L ‘ or tonnage used by foreigners. 
eternally or ‘ inter m P utl . n 8 both bulk and space from one measurement, taken 
nally, is exemplified by the diagram of midship section of a 
