Oct.  1,  1895.] 
Supplement  to  the  “ Tropical  AgricuUurisl'^ 
1 Imperial  pint  of  water  weighs  lbs. 
„ „ contains  20  tliiid  ounces. 
6 wine  bottles  are  reckoned  to  contain  one  gallon 
of  water,  or  26§  ounces  each- 
liainfall  and  Irrigation. 
1 inch  of  rain  is  144  cubic  inches  to  a square  foot. 
„ „ 1,296  „ „ or  4^  galls,  to 
the  .«q.  yard. 
„ „ 22,622galls.  to  the  acre (4,840 sq.  yds.) 
,,  ,,  113  tons  to  the  acre. 
,,  „ 144  million  galls,  to  the  .sq.  mile. 
By  an  inch  of  rain  is  understood  cus  much  rain 
as  would  form  a sheet  of  water  one  inch  deep 
over  the  surface  of  the  ground,  if  none  of  it 
soaked  into  the  soil  or  ran  off 
An  inch  of  rain  falling  on  a roof  will  be  after 
the  rate  of  a little  more  than  half  a gallon  to 
the  square  foot.  As  the  slope  of  the  roof  makes 
no  difference,  a house  roof  will,  when  an  inch 
of  rain  falls,  collect  a half  gallon  of  water  for 
every  square  foot  of  area  the  house  stand  upon. 
So  if  a house  is  40  ft.  long  and  30  ft.  wide,  I lie 
catchment  area  will  be  1,200  square  feet,  and  an 
inch  of  rainfall  will  supply  to  a clstein  600 
gallons,  allowing  some  15  gallons  for  waste  and 
evaporation.  If  there  is  20  inches  of  rainfall 
during  the  year,  then  with  projier  spouting  and 
cistern  room,  the  abovementioned  roof  or  area  will 
furnish  during  the  year  12,000  gallons  of  woiter. 
An  inch  of  lain  over  an  acre  of  4,840  square 
yards  being  22,622  gallons  to  the  acre,  it  is  a 
matter  of  some  interest  to  get  the  ajiproximate 
quantity  recpiircd  for  irrigating. 
As  1 find  that  usually,  even  in  a dry  season, 
after  2 inches  of  rain  have  fallen,  the  land  can  be 
idoLighed,  1 have  suggested  that  50,000  (fifty 
thousand)  gallomS  be  accejited  as  an  estimate,  the 
quantity  required  forirrigating  an  acre  of  land  once. 
Of  cour.-e  more  nr  less  water  will  be  required 
according  to  the  nature  or  staple  of  the  soil,  its 
dryness  and  powers  of  absorption.  But  still  it  is 
well  to  have  a definite  or  ajipro.vimate  standard  of 
measurement  as  to  the  quantity  of  waiter  required, 
to  be  delivered  by  a }>ipe  or  furrow,  or,  it  may  be 
pumped  for  irrigation. 
lit  Spain  the  regulation  quantily  of  water  for 
one  irrigation  is  2|  inches.  This  would  be  52,210 
gallons  per  acre. 
It  has  been  found  in  practice  that  one  good 
watering  is  much  better  than  two  or  three  light 
ones.  For  unless  the  water  .soaks  some  way  into 
the  ground,  it  does  not  enable  the  crop  to  feed  on 
the  plant  food  in  the  soil.  If  only  a little  below' 
the  surface  is  kept  moist,  the  roots  of  the  plan(.<! 
will  be  encouraged  to  grow  near  the  surface  and 
suffer  from  the  heat  and  drought,  instead  of  peiu- 
trating  deep  into  the  soil  and  sub-soil. 
Pleasuring  the  delivery  of  water  as  to  quantity 
supplied  in  a given  time,  has  been  a question  of 
some  consideration,  enquiry,  and  e.vperiment. 
The  factor  difficulty  to  be  dealt  with  i.s  that 
the  quantity  of  water  delivered  over  a weir  or 
through  a pipe  or  any  other  kind  of  ajierture 
constantly  varies  with  depth  or  pressure  of  the 
head  of  water  whence  it  is  derived. 
For  in.stance,  the  quantity  of  w'ater  wh  cb  is 
delivered  through  a four-inch  pipe  with  two  feet 
of  water  above  the  orifice  will  be  354  gallons  per 
mbiute,  while  the  quantity  delivered  through  the 
same  pipe  with  a head  of  one  foot  of  water  would 
be  only  250  gallons  per  minute,  being  a difference 
of  1,240  gallons  per  hour, 
29  r 
So  the  problem  to  be  solved  was  to  invent  or 
arrange  some  plan  by  which  tlie  water  should 
always  be  delivered  under  the  same  pressure 
w'hich  would  be  secured  if  ahvays  the  same  head 
or  depth  could  be  maintained. 
In  Italy  this  water  measurer  is  called  a modwle. 
The  principle  of  which  is,  that  a stone  trough  is 
filled  from  the  canal,  river  nr  spring,  in  which 
trough  or  module  the  wuiter  is  always  kept  at  one 
state  of  fulness  or  level,  and  so  maintains  tlie 
same  jn-etsure  and  consequently  delivers  e.vactly 
the  same  cpiantity  of  water  at  all  times  and  in 
l)crpetuit.y. 
In  the  United  States  of  America  the  law'  of 
water  delivery  provides  for  the  construction  of  a 
“ module.” 
Water  is  sold  by  the  square  inch,  that  is  the 
quantity  which  wdll  be  delivered  liy  each  square 
incli  of  the  a]ierture  through  wdiich  the  water 
ffows.  An  orifice  one  foot  long  and  two  inches 
high,  thus  delivering  24  inches. 
The  law  provide.s  that  “ water  sold  by  the  inch 
by  any  individual  or  corporation  shall  be  measured 
as  follows,  to  w'it,  every  inch  shall  be  considered 
equal  to  an  inch  square  delivery  orifice  under  a 
five-inch  pre.'Sure,  and  the  five-inch  pressure  shall 
be  from  the  top  of  the  orifice  of  the  bo.v  (module 
to  the  surface  of  the  water.”  This  will  give  a 
constant  pressure  of  four  inche,®, 
A module  thus  constructed,  and  with  this 
pressure,  will  deliver  through  erery  septare  inch  of 
the  orifice  74  gallons  (Imperial)  every  minute, 
and  450  gallons  jier  hour. 
A four-inch  jiipe  under  the  same  pressure  will 
deliver  94  gallons  per  minute. 
L.4W8  OF  CEYLON  RELATING  TO 
AGRICULTURE. 
Cl  I PTE  R X . — M iscellaneous. 
1.  As  it  i.s  necessary  to  have  channels  of  drain- 
age, ponds,  and  t.inks  unob.strncttd,  jilans  or 
.surveys,  made  under  the  authority  of  the  Surveyor- 
General,  in  which  encroachments  shall  appear 
shall  be  considered  conclusive,  unless  satisfactory 
proof  to  the  contrary  shall  be  established. 
2.  It  shall  be  lawful  for  the  Government  Agent 
to  order  verbally  or  in  writing,  any  person  ob- 
structing or  encroaching  upon  any  watercourse, 
pond  or  tank  within  his  Province,  to  remove  such 
ob.strnction  or  encroachment,  or  to  abate  it.  And 
if  the  pers(/ii  who  is  so  ordered  sh  11  fail  to 
com])ly  with  the  same  wi.'hin  a reason.ible  time 
or  if  there  be  any  doubt  as  to  who  i;  ibe  ]>roper 
])orson  to  whom  .■-uch  order  should  be  given,  the 
Government  Agent  m.iy  cause  such  obstruction 
to  be  removed;  and  I lie  Government  .4o-ent,  or 
an^  ]iei son  authoii.'-ed  by  him  in  writing,  may 
use  all  reasonable  means  such  as  may  be  necessary 
for  such  removal  The  Government  Agent  may 
recover  the  costs  buna  fide  incurred  in  effeciin'o 
such  removal  from  the  party  who'e  non-com])li- 
ance  wirh  oialers  caused  such  costs,  in  manner 
provided  in  Chapter  IX.  of  this  Ordinance. 
3.  I f a ny  per.sou  by  ele.iring  oi'  draining  any 
land,  b^  doing  any  act  wbatsoei'ci' on  the  same, 
shall  cause  uny  channel,  wuitercourse,  or  ela  u.sed 
for  irrigatiou  purposes,  to  be  blocked  up,  or 
obstructed  by  silt,  earth,  or  other  substance,  it 
Bhall  be  lawful  for  the  Government  Agent  of  the 
