quantity of timber.

295

ADVOCATE , on INTERNAL imrnovnmnnrps.

web is, not composed of one complete tim-l ’l1GI‘B MB 10Cl<S 011.1110 Cofitllient‘, of large  ST, KATH,,mNE’s DOOKS

ber, bu:t.\‘th_at the fibres are disnnited at the llmensions, \vl'iere the angle is con.<ideri- W,,.i,h ,,f,he10Ck 45 f
point cit’ meetiiig, and consequently if‘ that hly less, which have stood perfectly well. 'p*m~ec,,On - 11 eel‘
part foin any«._cause should become flatten- The angle of the celebrated sea-lock of R,,,Ji,,,S Of,1,ega,e 1]-7 —

ed there are no fibres to resist the trans.,

verse strain thus produced ; and as the flat-
tening ot’ this part ‘of the arch is an efleci
which might probably arise from any yield-
ingof the abutmcnts, or Wear of the heel
posts in the hollow quoin, this would evi-
dently be the weakest part ofthc curve. It
therefore becomes necessarv to deviate in a
small degree from the true curve of the
arch, by giving the gates greater length,
and causing them to meet at a ‘point a short
distance From the curve, or in fact rendering
them slightly Gothic; but as the security to
the point is obtained at the expense (if a
constant transverse strain upon each of the
gates, the deviation from the true arched
figure s’ioul-cl be as little as possihie, coiisis

ite itly with the object in view, and by no

mcans__so gi'ea,t.as is commonly employed in
lock gates: lsliiould think a devizition ofonc
foot or eighteen inches quite sufficient for
the purpose of locks of from forty to fifty
feet wide.

Geneml Remm-7:3.

It. was my intention to have concluded
the preceding part of the article with :1 Ta-
ble of'.the requisite dimensions of timber for
gites ol'_ ditfereiit sizes, both of the curves
commonly employed, and of’ those which l
should; recommend; I find, however, that
tnese calculations would require a greater
lengtlifof time than I can at present devote

to the subject, aridl therefore conclude witn .

a few-general 1‘eina_pks on the results arriv.
ed at. ;_ H‘ V.‘
In the first place, with respectito ihi.--
proper,» eiiigleof sir-aighi gates, this being 21
Stlbjecll1¢g,Il..l1'E\ll.\’ calculated to excite that
propen'_sit'ies of the‘ 1'l'l2tll1HIlt.UlClt\l'l to se.
l’llS_ln'1Xlll'ia and l1'llI1’1lU1t-L to work, a gl'(?iL!
nuinberof soluiions,to the problem liaw
been given ; but I Inner. reinarlc, with eve
ry respect for that useful class cfirieii, than
they are frequenly too .an:~:ious to com
m'~nee ini*esiig-aiioiis without suthcierr
clan, and coiiseqiiemly arrive at resuli.~
totally incoi'i'ect., which has certainly been
the case in those investigations 1 havi-
hurl an opportunity of examining ongihe
SL1bJr3Ct.

It seems to me perfectly in‘ipossllJle to
arrive at correct results, without first a~-
ceriainiiig the amount of traiisverse strain
piioducucl’ by the enalpressiire, which doe.-
not seem to have beendone before;*biiI
having obtained this fiom Gll'fil‘i'llS;eXpB1'l-
ments to be one-tenth of il1e~efi'eet of-' an
equal weight in the rniddle of the len_~gi‘h.
I have little doubt that the arigle 19";'.‘25
would be found, by experiments,’ to be ve-
ry nearly that in which the g1‘ente$‘=
strength would be obtained with a given

The angle commonly adopted in thio
country, is considerably more 'h-an 19‘
25', amounting generally to bet\VeBl1 30
and 40 degrees, which is said to be pre
ferred from the direction ofthe thrust being
met by a large quantity of brickwork. 1
cannot, however, conceive this to be a mat-*
ter of much importaiice, particularly as

.VIuyden is only 16° 30’, and the ancient
lock of Sparenrlain, which was builtiin
‘I568, and has stood many storms WllhOI1'
injury, has a sally of not niorc than one-
slXlel3l'1l.l‘l 2-the angle Ol]gl1t‘C€‘,l‘lz1l1ll_y to
be in seine measure guided by ihacircum-
stances in which the gate is placed; at
the same tirne, I consider the angle coin-
_monl_v made use of in England, (0 be dc»
cirledly larger than necessary, and a use

increases one of the evilsof canal naviga-
t.ion,—-the time consumed in passing the
locks * ‘

The employment of curved timber is un-
douhteilly advantageous, but its applica-
‘ion is eviclemly made ii,ion nn fixed prin
cfiplcs, as inay be seen from the iliitiweiices
of the curves which lli\V" lJt‘I~l'li?l.(‘ll)}1)lG('l;
‘Q1110. being so great as to vi-ry nearly ap
preach the figure I have poinied out as the
best, while others are so exceedingly flat
that they possess little ad raiitage over ihe
straight. gate.

To illi.isti'-ate these clifl’ei‘ences_ in wood-
en gaies, I have represented, in the accom-
pying drawing, the curves employed in thr-
gutes oft the St Kail‘iai'ine’s, Lond_oii:"'{iiii‘l
West India Docks. The 'di_niensions are
as follows :—— 

less Weight of inaterial employed, Wl'llCll ‘P,.Ojec,i“n

 

Consequently the angle qJ== 29° 16’,
ancltl __-—.-_ 6° 8', .

LONDON DOCKS.

Width of the lock. 40 feet-
Proj~ction 9
Radius of the gate 50

Angle Cp 2 23° 35’, and 6: .13"..54’.

‘VEST INDIA DOCKS.

Width of lock , 45 rear.
. _ . 10
' Radius ofihei gate  I20
Angle tr: 2 26° 24’, and 6--5-"~ 53’.

have calculated the amount of transverse
strain in each case, (halt the pressure of
water upon one gate bein: iiuii_v,) and the
c~uii'ie, if hey were of s!1‘alghI l.ll1‘ilIeI', hav-
ing an equal salient angle.
itl‘€a.l‘1"t1t\gt‘(l. in the following Table.

ln order to make the corriparison of the

is also added a column of the amount of
lrdllr“-V(~‘1‘SB strain on the latter, that on the
straigh gdl(3‘lJEll'lg‘1l‘lll y. . i K .

The fourth roluirn illustrates the reduc-
tion ofihe flllI!([l.~'l01'lS of square timbe-
which int-iy be,pei‘iriitied owing to the dir

  TABLE iii.

ininished strain. “

 

It ihiis ri?ppe:ii‘s that (‘0nsiderablei advan-
tage is gained in each case fioin the cur-'
vaiui'e, but ,_I:hdt. in the London Docks,
froin the l'£\(ll|.S being’ less, and the [Wu

 

   

 

.-n‘Afl*’JA‘ '1»
, yr... 
 ---- ~   -A «Transiierse s‘trai.n Ti‘aiis.V«3..l':.( .5.tF*l1J..Dl1}.l.€§£5.l9l15....,-i i
of strai£‘l'iI rim that on the timber having
Transverse _ ~' , - ,1 0. , 1 0. h
. . _,_ bei having the siriiigii. ,__a.e equa strengt .
C-‘IATIL. s:r‘z1l[1,£tI)b€- Same SR1-mu, be-mg un’,,y_ - mm On the
i ‘mg Llnuy‘ Hnglp,  iw be i straight Eillfi
ing unity. Ming “HWY-i
Alb‘t.Ka!l1arine’s ,
Docks, _ '86 1 178 '73  90g
‘ London Docks, '56 1.229 '45 ' gas
West India‘Docl{s '86 1.201 '72 Q‘ X
.‘ 1,». . ,. i , k _ ‘Viki

gancfi nearly as flat as in the West India.
and St Ka‘~.harine’s D.icl<s.
The following are the dimensions 2....

CALEDONIAN CANAL.

-_'jai.es in consequence approaching nearer '. pg-,d,_h ofme 10¢}; 40 feet.
the curve of a complete arch, the advan Ammm, of P,.,_,j,3_,,,',on 10 in
age is I11U_C_l1'gl'ea.‘E‘.1', and the transverse; Rtldms of c,,,.,.,,,,,,.e »  75

strain ' ’5onsequence rediiced to less than Angle of sally (P =_— 30°, and 6 r‘;=&f:3’
hal iat.of,straight gates having the same DUNDEE DRY DoCKs_ , ______,;‘9g.
5"“1‘°“”“g1e' . . . ’ Width oifentrniice 40 feet.

I ‘ _ , -

‘mm dlflicuhy of Oblammg umber of Sufi ‘ Aiiiountiof projection 7 feet 6 inches.
jficient Cu1‘Val..Lll’Q has liu-‘en 1.I.1‘,€..teC1 as it re?! Ra,.,i,,S O,-,,,,,,,,,,‘,~,,m,_m . __57 feet,
3.011‘ for the flatness ot:i_l1e~ciirves_,ernploycd Amrle of Sam, (P _»_;_: 22o§i,,,,a,,d 9 i: 90 12:.
.n wooden gates ;. this is certainly a con— ° s'HEERNEss--BAsm.._;__v,H ;
.5lClE.l‘a.llD11 which must be attended to, but ; 58  t

. LS siinilar*cui‘\'es are employed when the Width of entrance 1‘) feet.6 ‘n E.

'“““3‘.."."5‘.l_.‘..‘?“de use We eat l”‘.’“= 1 Cm“ A*“°.““‘ °‘ P"°?“‘°“.°“ .33 £2} V . ~..ir»i»”¢‘~
(:Ol'lCl’lVe this to be a point which has nia- Radius of CUlVd.i11l8 ~ ieo 55

eri-ally influenced the choice of the figure.

In the accompanying drawing (Plate
VII.) are given the curves of the gates of
he Caledonian Canal, the Dundee Docks
and Sheerness Basin, which are of cast
iron :. they will be found to differ very ma-
terially fronyi-each other, being in one in-

4

l
I.

Angle ip _—= 24° 5’. and 9
To make a comp-,irison,of these curves,
I have calculated a Table, as in the ease
of the wooden gv.tes,comaining the amount
of the transverse si rain which straight
gates would have under similar circum-

stances.

Willi the aid of the preceding: iformiilee, I,

These foijinnlaa ’

straight and curved gate more direct, there’