73^ 
THE  TROPICAL  AGRICULTURIST. 
[May  1,  1897. 
The  Rajawelle  Estate,  situated  in  the  lower  Doom- 
bera  valley,  is  known  to  lie  within  the  line  of  country 
in  which  the  S.  W.  Monsoou  occasionally  fails,  and 
the  result  is  that  this  Estate,  which  in  moist  seasons 
bears  very  heavy  crops,  loses  in  a very  dry  season 
from  one-third  to  one-half  of  the  crop  on  the  trees. 
There  are  only  two  or  three  small  streams  in  the 
property,  and  even  these  in  very  dry  years  occasionally 
cease  to  How  ; but  the  Mahavilla  Ganga  forms  the 
boundary  of  Rajawelle  on  the  south- side,  and  as  the 
Mahavilla  affords  at  all  seasons  an  abundant  volume 
and  fall  of  water,  the  idea  occurred  to  the  proprietors 
of  the  Estate,  to  make  that  river  itself  subservient  to 
the  purposes  of  irrigation.  The  problem  praotically 
was  a serious  and  difficult  one.  The  old  Estate  lies 
a mile  and  a half  from  the  river  in  a straight  line,  and 
is  divided  from  the  new  Estate  by  a ridge  ascertained 
by  actual  survey  to  be  460  feet  in  vertical  height. 
The  power  requisite  for  raising  even  a moderate 
quantity  of  water  to  this  high  elevation  by  a single  lift, 
is  very  great ; yet  the  necessity  for  employing  a single 
lift  could  not  be  avoided  except  by  substituting  still 
more  costly  Machinery,  such  as  a powerful  Steam 
Engine  half  way  up  the  hill.  To  this  there  were 
many  practical  objections.  Accordingly  it  was  resolved 
to  throw  up  the  whole  quantity  of  water  required, 
by  means  of  the  power  obtainable  from  the  river  alone  : 
and  after  consulting  practical  Engineers  in  England 
and  Scotland,  it  was  resolved  to  employ  as  the  motive 
power  ^Vhitelalo' s Horizontal  Water-wheel.  This 
Wheel,  with  the  Pumps  and  connecting  Machinery, 
has  been  accordingly  manufactured  by  Messrs.  White- 
law  at  Glasgow,  and  the  whole  are  on  their  way  to 
Ceylon  in  the  ‘ Coromandel.’  The  iron-piping  (of  the 
length  of  6,250  feet  and  weighing  212)  Tons  intended 
for  the  conveyance  of  the  water  over  the  ridge  was 
brought  out  by  the  ‘ Armais’  some  weeks  ago  ; and  we 
believe  a great  part  has  been  forwarded  to  Rajawelle. 
The  works  at  the  latter  place  are  in  rapid  progress, 
The  great  sluice,  for  supplying  the  water  to  the 
Wheel,  is  nearly  cut.  This  sluice,  which  will  be  a 
small  Canal  when  completed,  is  to  be  nearly  three 
quarters  of  a mile  in  length,  and  eighteen  feet 
broad  by  three  feet  deep,— discharging  at  least  half 
a million  of  gallons  of  water  per  minute.  As  there 
are  several  rapids  in  this  part  of  the  Mahavilla  Ganga 
(indicating  of  course  a great  declination  in  the  bed 
of  the  river)  a comparatively  short  extent  of  sluice 
gives  a great  fall ; — consequently  it  is  found  that 
the  three-quarters  of  a mile  give  a fall  of  some  24 
feet.  The  large  body  of  water  supplied  by  this  canal, 
with  the  fall  of  24  feet,  produces  a very  large  amount 
of  motive  power ; in  fact  it  is  calculated  to  be  equal 
to  a Steam  Engine  of  about  200  Horse-power.  We 
believe  that  a Steam  Engine  of  this  size  would  have 
cost  more  than  the  whole  expense  of  the  intended 
works, independently  of  the  objection  that  its  work- 
ing would  have  been  very  costly,  whilst  the  Water- 
wheel is  self-acting. 
The  Wheel  will  oe  quite  a curiosity  m its  way. 
The  Diameter  is  only  14  feet,— a size  which  would 
be  considered  small  for  any  of  the  "Watei -wheels 
used  on  Coffee  Estates  for  working  Pulpers  and 
Clerihew  fans.  Wo  believe  that  the  ordinary  over- 
shot Wheels  used  on  Estates  are  about  16  feet  in 
diameter;  but  the  resulting  power  is  seldom  more 
than  from  8 to  12  Horse-power,  An  overshot  Wheel 
of  200  Horse-power,  would  require  to  be  at  least 
sirJi/  feet  in  diameter ; and  a Wheel  of  such  an 
unvvieldy  size  would  have  required  to  be  very  favor- 
ably placed,  as  regards  the  supply  of  water  and  other 
circumstances,  to  be  worked  effectively.  We  re- 
member seeing  a skctcli,  in  the  Illustrated  Hews  last 
year,  of  a gigantic  wheel  of  this  description,  lately 
erected  at  some  Minos  in  Wales,  but  although  the 
diameter  was  four  or  live  times  as  groat  as  that  of 
the  Rajawelle  Water-wheel,  the  effective  power 
was  loss.  Mr.  Whitolaw  himself,  in  a letter  pub- 
lished in  the  Mechanic’s  Magazine  of  May  6th  1854, 
Speaking  of  this  very  llajawelle  Wheel,  describes  it  as. 
“ A Water-wheel  of  200  Horse-power,  which  I am 
“ making  for  Messrs.  Gwynne  & Co,,  Engineers, 
■“  London,  which  is  to  work  six  single-acting  pumps 
f of  20  inches  stroke  and  8J  inches  diameter,  to  raise 
“ water  to  a height  of  460  feet  for  irrigating  an 
“Estate.  When  finished  I believe,  no  water-wheel  in 
“the  world  will  he  of  rj  reate  r power  than  this  \ but  be 
“ this  as  it  may,  it  will  be  a large  one.’’ 
The  principle  of  Whitelaw’s  Wheel  is  peculiar  and 
not  very  generally  known.  It  is  placed  horizontally, 
and  as  a central  opening  for  the  ingress  of  the  water 
from  the  sluice,  which  is  supplied  by  a large  in- 
duction pipe.  The  diameter  of  the  pipe  for  supply- 
ing the  Rajawelle  Wheel  is  76  inches,  so  that  a tall 
man  with  his  hat  on  miyhf  stand  uprifjht  in  it  ! This 
pipe  will  be  always  full  ; and  even  persons  practi- 
cally unacquainted  with  Hydro-dynamics,  can  readily 
understand  that  an  enormous  force  must  be  exerted 
by  a perpetual  column  of  water  six  feet  four  inches 
in  diameter  and  twenty-two  feet  in  vertical  height. 
The  principle  of  action  is  somewhat  complex  in 
theory,  though  extremely  simple  in  practice  and  re- 
sult. It  has  been  described  as  “centrifugal”;  and 
so  it  is  to  a certain  extent.  The  arms  of  the  Wheel 
are  curved  and  have  orifices  at  the  extremities ; 
and  the  water,  forced  in  through  the  central  opening, 
rushes  through  these  curved  arms  and  out  of  the 
orifices;  and  Mr.  Whitelaw  describes  the  action 
as  communicated  by  the  water  pressing  on  the  sides 
of  the  arms  as  it  rushes  through  and  by  the  centrifugal 
force  as  it  rushes  out.  But  as  we  observe  from  the 
drawing  which  has  been  sent  to  us,  that  '.the  dia- 
mater  of  the  central  opening  in  the  Wheel  is  very 
much  less  than  the  diameter  of  the  large  supply  pipe, 
we  fancy  that  the  action  is  greatly  aided  by  the 
operation  of  another  : valuable  hydro-dynamical  princi- 
ple, viz.  that  a force  exerted  upon  a certain  surface 
of  water  is  multiplied  lohen  communicated  through  the 
loater  to  a smaller  surface.  The  increase  is  in  a known 
ratio,  viz.  inversely  as  the  squares  of  the  surfaces. 
This  is  the  principle  of  the  hydraulic  press.  It  was 
by  the  application  of  this  principle  that  Mr.  Robert 
Stephenson  raised  the  vast  tubes  of  the  Britannia 
Bridge.  On  a small  scale,  the  action  of  a common 
“syringe”  is  precisely  the  same;  and  this  perhaps 
is  the  humblest  illustration  of  the  principle. 
The  Rajawella  Wheal  is  to  work  three  or  more 
Pumps,  which  ai'e  upon  the  ordinary  principle,  and 
no  further  remarkable  than  for  their  size  and  strength. 
These  pumps  will  deliver  their  water  into  the  conduit 
or  long  iron  piping  laid  over  the  ridge ; and  Messrs. 
Gwynne  & Go.  have  guaranteed  that  the  Machinery 
shall  deliver  500  gallons  of  water  per  minute  at  the 
top  of  the  ridge,  which,  as  mentioned  above  is  460 
feet  in  perpendicular  height.  To  give  an  idea  of  the 
strength  of  the  valves  required  in  these  pumps,  it 
may  be  mentioned  that  the  actual  weight  of  the 
water  in  the  conduit  pipe  when  full,  will  be,  in  round 
numbers,  over  seventy  tons  ; but  as  tbe  pressure  exerted 
by  a column  of  water  is  proportionated  only  to  its 
vertical  height,  the  effective  weight  may  be  taken  at 
one-tenth  of  that  figure.  A continual  pressure 
however  of  even  7 or  8 tons  upon  pump-valves,  calls 
for  both  stout  material  and  good  workmanship. 
How  much  of  the  Rajawelle  Estate  can  be  watered 
efficiently  by  the  amount  of  water  above  stated  (500 
gallons  per  minute)  is  a question  which  actual  experi- 
ment alone  can  solve.  Much  difference  of  opinion 
exists  on  the  subject.  Some  of  Messrs.  Tytler  and 
Morton’s  friends  are  kind  enough  to  assure  them 
that  the  whole  thing  will  be  an  utter  failure  1 The 
Estate  consists  of  700  acres  or  thereabouts,  of  which 
200  Acres  (the  old  Estate)  lie  over  the  ridge,  and 
.500  Acres  (the  new  Estate)  between  the  ridge  and 
the  river.  Taking  600  trees  to  the  acre  on  the  old 
Estate,  and  1,200  trees  to  the  acre  on  the  new  the 
total  number  of  trees  may  be  set  down  at  720,000 ; 
and  this  happens  to  bo  exactly  the  number  of  gallons 
of  wator  per  24  hours  at  the  rate  of  500  gallons  per 
miuuto.  1 ! other  words,  if  the  whole  Estate  is  to 
be  watered  at  once,  the  quantity  received  by  each 
tree  would  be  only  one  gallon  in  the  24  hours ; and 
this  without  allowing  for  loss  by  evaporation,  d’C. 
But  we  believe  the  intention  is  to  water  only  50 
or  100  acres  at  a time;  and  it  is  calculated  that  in 
about  a month,  the  greater  part  of  the  Estate  would 
have  received  a supply  equal  to  a heavy  shower  of 
rain.  In  1853  the  drought  at  Rajawelle  lasted  nearly 
