102 



THE AGRICULTURAL NEWS. 



May 24, 1913. 



•which, as has already been pointed out enters into 

 ^he fundamental relationship that exists between 

 •rainfall and the yield of crops. 



In a somewhat narrower aspect the importance of 

 rainfall records is eviiicid by comparing, every season, 

 •yield and precipitation on individual estates. During 

 a, dry season, or a very wet season, certain lines of 

 -expei.iliture in estate manatjeniput will be lo>i'er 

 "than when the weather is normal. < )tlier.-i, < if course, 

 will be higher. '!"he systematic observations of the 

 'jain received are therefore useful as a check on the 

 apportioimient of circulating capital; and although the 

 Application in this way is often unknowingly recognized, 

 its acknowledgement as a definite correlation would 

 •■appear to be by no m^ans general. 



There is often some doubt cast upon the reliability 

 <}{ rainfall rpcords — not that the actual observations are 

 inaccurate, but rather the circumstance as to whether 

 rain gauges on large estates are placed in such positions 

 ^8 to ensure a truly representative estate record. On 

 those plantations, for instance, which run down to the 

 seashore, it makes the greatest difference if the 

 j-ecording instrument is placed on or near to the 

 coast, or higher up on the estate. For one thing, 

 *he actual rainfall is liable to be much less near 

 the sea; and in the second place, the degree of ex- 

 posure to wind may mean that the gauge in such 

 s. place will receive less water than one in a more 

 sheltered i)osition, even though the precipitation is 

 ■ «xacily the same in each case. This point is not a new 

 •one. It has been critically considered in investigations 

 to find out whether forest-clad laud induces more rain- 

 fall than land which is bare, and the question may 

 yveW be regarded with care in this its uiore limited 

 • •-aspect. 



In the West indies nuich of what has been said 

 above is dirrctly applicable, though a consideration of 

 the rainfall in these colonies brings out several 

 points of unique interest frequently absent in large 

 continental tropical countries whoe conditions are 

 more stereotyped. Alluding, for instance, to the ques- 

 tion of the effects of forests on rainfall in the West 

 Indies, the statement has been made that rain clouds 

 which ajjproach more or less Hat islands like Antigua 

 or Harbados fre<juently rise and split, or retire in an 

 erratic manner out to sea. The presumable explana- 

 tion of this curious phenomenon is that the heated air 

 rising from the land interferes with the natural pre- 

 <;ipitation of moisture by stimulating vaporization, ami 

 by setting up repellent air currents. The inference 

 <;annot be resisted that afforestation would actually 



have the effect of increasing the rainfall under such 

 conditions as the-'^e, and the idea would seem to warrant 

 the rapid acceleration of the afforestation movement 

 that has recently been started in many islands. 



Another curious feature in the West Indies ig 

 the 'Stalia' rain of St. Kitts, an island near to which 

 lies, some few miles off, the Dutch i.sle St. Enstatius — • 

 popularly known as 'Statia'. Reliable obser\ers say 

 that at certain times of the year, clouds can be seen 

 extending from the respective peaks in each island 

 across the channel. Eventually they should meet. If 

 they do not meet there will be no rain. If they do, the 

 land around the coast receives the shower which for 

 for some hours the local observer has confidently 

 anticipated. 



There are other features of West Indian rainfall — ■ 

 generally <pnte local ones — which are of very great 

 interest to those they immediately concern. These 

 may be dispensed with here, however, and we may con- 

 clude with a few references in regard to artificial water- 

 supply and rainfall. 



Common observation shows that there is a pronoun- 

 ced difference in the benefit derived from a sharp shower 

 in the Tropics and prolonged watering or even irrigation. 

 Why natural rainfall should be superior can be explained 

 on general physical grounds, but the explanation does 

 not appear to have been entirely established by experi- 

 ment. The kinetic force of tropical rains causes more 

 rapid penetration, and also, the shade, and the satura- 

 tion of the atmosphere check evaporation. Undoubt- 

 edly some of the gases carried down by rain exert 

 a useful infiuence: gases like oxygen, nitrogen, oxides 

 of nitrogen — the latter being common after thunder- 

 storms — and even carbon dioxide may have some use- 

 ful action on the unavailable food supply' in the soil. 

 Also the temperature of the rain may be felt. Consid- 

 ering the large quantity of water that is usejd in 

 gardens in the West Indies, an experimental investiga- 

 ti<m of the subject would no doubt be of value, in that 

 it would help to provide ways for reducing the big 

 demand on local supplies that are not always constant 

 enough to stand it. 



DEPARTMENT NEWS. 



The Imperial Conunissioner of Agriculture is due 

 to depart for England, on duty leave, by the R.M.S. 

 'Magdalena' on the 2.Sth instant. Dr. Watts will 

 conduct official business in England, and will confer 

 with the (Colonial Office on matters pertaining to 

 West Indian agriculture. 



