252 
THE  TROPICAL  AGRICULTURIST. 
[Oct.  I,  1895. 
ihe  one  wliich  wouM  prol>ably  i)ro(lnce  tlie  largest 
saving  of  cost  with  the  least  amount  of  injury” 
and  accordingly  he  made  the  characteristic  curve 
wliatitis  beyond  Nawalaintiya,  one  of  5-chains  ra- 
tlins. That  he  was  right  we  will  not  say,  in  advising 
5-chain  curves,  but  his  view  of  the  clTect  on  cost 
of  construction  was  amply  proved  Ijy  Mr.  McNair’s 
surveys  .and  estimates,  according  to  which  on 
the  line  in  question  a dillerence  of  T.37  cli.ains  in 
the  limiting  radius  of  curve  made  a dilTcrence  of 
Kl0,0OU  a mile,  tlieline  being  in  every  other  rt*- 
spect  tlie  same. 
Queensland  supplies  .another  example.  Tlie  Ijis- 
wich-Toowoomba  r.ailway,  78  miles  in  length,  w.as 
in  the  first  instance,  .surveyed  for  a 4'’8.y'  track 
M'ith  a char.acteristic  curve  of  S’19  cli.ains,  the 
dimensions  .adojited  in  the  older  colony  of  Jvew 
South  ^Yales.  The  cost  being  found  prohibitive, 
a new  trace  was  surveyed  for  a .3' '6"  railway  of 
the  same  quality  but  with  a minimum  curve  of 
5-chains  radius.  This  w.as  built  by  Messrs.  Peto, 
Rrassey  (.t  Petts  at  a total  cost  or  34°o  less  than 
the  estimate  for  the  wider  line,  while  on  the 
mount.ain  section  where  the  line  crosses  the  Little 
l.iverpool  and  Main  ranges  the  saving  was 
ne.arly  70%.  The  Little  Liver])ool  r.ange  700', 
and  the  Main  langc  1400,  above  the  level  of 
the  surrounding  district  are  cut  up  into  long 
thin  spurs  with  deep,  narrow,  steep-walled  r.avines 
intervening  ; perhaps  as  dillicult  a bit  of 
country  from  .an  engineer’s  ])oint  of  view 
.as  any'  in  the  world  ; the  kind  of  country  where 
.a  (litTcrence  of  .a  chain  in  railius  of  curve  makes 
an  enormous  difference  in  cost  of  construction. 
In  this  ease  close  surveys  .and  estimates  showed 
that  in  the  item  of  vi.aducts  alone  a reduction 
from  8-i!)  to  5 cli.ains  would  effect  a reduction  in 
cost  of  no  less  th.an  £29,000  per  mile  on  the  22-iuile 
.section  (1865  prices). 
Much  of  what  has  been  said  under  the  he.ad 
of  curve  and  gauge  might  with  cijual  propriety 
have  been  said  under  the  he.ad  of 
ALIGNMENT  AND  GAUGE. 
We  have  .seen  why  and  to  what  extent  sharp 
curves  are  less  injurious  the  narrower  the  track. 
With  a grip  on  tlie  practical  corollary  therefrom, 
namely  that  sharp  curves  may  be  more  freely 
used  in  setting  out  a metre  gauge  railway  than 
one  of  5'  6",  there  should  be  no  ditHculty  in  ap- 
prehending the  following  crucial  propositions. 
First,  that  except  it  may  be  in  crossing  a billiard 
table,  tlie  .alignment  to  a bro.ad  g.auge  will  rarely 
coincide  with  .an  .alignment  to  a narrow'  gauge,  the 
divergence  being  grc.ater  the  more  broken  the 
country,  the  more  closely  it  resembles  the  spur 
and  <'iilly  type  of  formation.  Second  that  a com- 
parative 'est'im.ate  of  the  cost  of  a narrow'  gauge 
r.aihvay  to  the  alignment  of  one  of  bro.ad  gauge 
is  unfair  and  fallacious  ; and  the  more  fallacious  the 
more  dillicult  the  country  to  be  traversed.  A metre 
track  shouUl  be  allowed  to  pick  its  w'ay,  and  to  tal<£ 
full  advantage  of  the  greater  facility  with  which 
it  can  mould  itself  to  the  n.atural  contours  of 
the  ' surface,  and  thus  elude  the  nece.ssity  for 
tunnels,  cuttings,  lofty  embankments,  and  the 
lorn'-  culverts  w'hich  lofty  embankments  ent.ail. 
To  "coerce  a narrow  gauge  railway  to  the  res- 
tricted alignment  of  one  of  wider  type  is  to 
throw'  away  a main  source  of  its  handine.ss 
and  cheapness. 
The  fallacy  should  now  be  obvious  which 
vitiates  the  cut-and-dry  method  cinployed 
iu  Westminster  to  calculate  tne  saving  in 
the  item  of  earthworks  resulting  from  a reduction 
of  •■■aiKm  : “ suhtr.actthe  cost  of  a par.allelogram 
of  'the”  width  of  the  difference  of  gauge  and  of 
the  depth  .and  height  corre.sponding  with  tluat 
of  the  cuttings  and  emb.ankments  ” — quietly  assum- 
ing, the  reader  will  note,  that  in  country  broken 
up  into  spurs  and  gullies  and  on  prairie  or  veldt 
as  smooth  as  your  Sund.ay  h.at,  the  alignment 
of  the  two  will  he  the  same  ! Where  an  oro- 
grajihical  survej'  is  .available  sufficiently  det.ailcd 
to  show  the  contour  lines  for  every  tenth  foot 
ot  altitude,  alignment  .and  quantities  for  a marrow 
gauge  line  m.ay  be  ajiproximately  workoil  out 
from  the  jdans  and  estimates  for  a,  broad  g.auge  ; 
but  where  as  in  Ceylon  no  such  datum  exists 
an  absolutely  independent  survey  is  indispensable. 
And  the  assumption  that  all  gauges  mii.st  travel 
from  terminal  to  terminal  by  exactly  the  same  route 
is  mislc.adiiig  with  respect  not  onlj'  to  earthworks, 
but  to  such  costly  features  as  tunnels,  viaduct.s, 
bi  idges  and  culverting  .also  ; how  misleading  may 
be  inferred  from  the  inst.ance  alre.ady  cited  of 
the  viaducts  on  the  Queensland  Southern  and 
Western  Kaihvay. 
GRADIENT  AND  GAUGE. 
Were  railw.ays  straight  and  level  throughout, 
locomotives  might  be  smaller  or  tniins  much 
heavier,  so  little  would  be  the  tractive  jiower 
reiiuircd — s.ay  from  6 lbs.  to  18  lbs.  jier  ton  of 
gross  weight  behind  the  engine,  according  to 
speed,  climate,  .and  conditions  of  road  and  roll- 
ing stock  ; w ith  about  thrice  this  pow'er  of  pull 
for  starting.  Hut  very  few  railw.ays  are  level 
throughout  ; most  have  ,a  very  appreci.ablc  per- 
cent.age  of  their  length  on  the  slope  ; the  Indian 
metre  lines,  for  instance,  have  about  2U  per  cent, 
say  400  miles,  of  their  united  length  on  gradients 
worse  than  1 in  200.  The  wm'st  gradient  on  a 
line  determines  the  weight  of  its  locomotives, 
.and  with  it  all  those  items  of  construction  .and 
mainten.ance  which  in  their  turn  are  ruled  by 
the  travelling  lo.ad. 
Hut  the  influence  of  givadients  does  not 
end  here  ; it  is  felt  in  cost  of  h.aulage 
also.  For  a gradient  adds  to  the  work  of  haul- 
ing the  train,  the  much  h.arder  .and  costlier 
work  of  lifting  it,  and  this  ata  r.ate  such  that  the 
vertical  rise  per  cent  of  distance  traversed,  the 
gradient  in  plain  phrase,  expres.ses  the  percentage 
of  the  train-lo.ad  added  to  the  resistance  of 
haulage  on  the  level.  Thus  if  the  re.sistance 
to  haulage  on  the  level  be  10  lb.  ]ier  ton  of  train- 
lo.ad,  a gr.adient  of  1 per  cent  (=one  foot  of 
rise  per  100  feet  length  of  r.ail)  would  .add 
22'5  lb.  per  ton  of  tr.ain  load  to  the  work  to  be 
done  by  the  locomotive  ; a gr.adient  of  2 per 
cent  (1  in  50)  would  add  45  lb.  ; one  of  2'5per 
cent  (1  in  40)  56  lb.  ; and  so  on.  Or  take  a 
locomotive  whose  weight  is  so  distributed  .as  to 
throw  18  tons  of  it  on  the  coupled  wheels. 
Then  reckoning  its  tr.active  power  .at  one-sixth 
the  insistant  weight,  and  the  tr.active  j)ower  re- 
quired jier  ton  of  train  lo.ad  on  the  level  at  10  lb., 
such  a locomotive  should  move  672  tons — on 
the  level.  Hut  now  see  the  reduction  of  haulage 
cap.acity  when  the  train  requires  to  be  lifted  .as 
well  as  (lulled  : On  a gr.adient  of  1 per  cent,  the 
locomotive  would  bo  equal  to  a load  of  no  more 
than  about  260  tons  ; on  one  ot  2 per  cent.  120 
tons  ; and  on  one  of  2'5  per  cent.  100  tons  only. 
In  view  of  these  facts  it  should  be  easy  to  un- 
derstand why  where  .a  heavy  traffic  is  to  be  ]iro- 
vided  for,  no  outl.ay  is  begrudgeil  to  secure  a level 
track,  the  saving  in  h.aul.age  and  uiikccii  more 
than  coverin  ;■  interest  on  the  extra  capital  thus 
exiiended.  Oil?  concerH,  however,  is  with  cases 
of  light  traffic,  with  c.ases,  therefore  w’here  the 
limit  set  to  capital  cx])cndilure  by  the  jirospec- 
tive  returns  is  soon  reached.  Here  the  ludme 
consideration  is  a cheap  line,  and  sharp  curves 
