154 



TBINIDAD AND TOBAGO BULLETIN. [XVIIL :i. 



It is the object of the present report to inquire more fully into this 

 supposed relation, and to see how far the various statements are 

 justified by the experience of a longer series of years. 



It is recognised that the rainfall may have effect in a number of 

 different ways. Early rains in May will result in the broods being 

 earlier ; a sudden, as opposed to a gradual, start of the wet season will 

 cause the broods to be more distinct ; late rains in December and 

 .January will produce a partial fourth brood and may cause many eggs to 

 hatch that would otherwise have passed over till the following wet season. 



We are concerned here more particulai-ly with the total amount of 

 '• blight " or " damage " in each year in relation to the rainfall. 



The records of previous observers have been freely used and their 

 contribution is gratefully acknowledged. 



GENERAL RELATION BETWEEN RAINFALL AND CROP. 



The strength of a chain is limited by its weakest link ; in the same 

 way the production of any crop on any particular piece of land is 

 limited by the most unfavourable condition affecting that crop. 



This condition may be one of many— temperature — rainfall — wind- 

 chemical condition of soil — physical condition of soil— drainage, &c. 

 Whatever the limiting or determining factor may be — and it may be 

 different in different places or even in the same place in different years — 

 the yield of the crop will directly follow changes in the limiting factor. 



We should expect, then, to find the most distinct correlation between 

 the sugar crop and rainfall in countries where the rainfall is low and has 

 become a limiting factor. 



Such a condition is found, for example, in the island of St. Croix 

 where the rainfall is seldom above 40 inches. Fig. 1 shows the close 

 relation that exists between the crop and the rainfall for the years 1891 







To! 



.10 



L 



y 



s*- C 



roLx 



/tar-:' 



?oooo. 

 i5;ooo 



4 



10,000, 



Jooo" 



* ■ 



i 



Fig. 1. 



Fig. 1. Annual iaiufnll and sugar crop in St. Croix 1800- HO-J .sliowin- close 

 (ic))L'nilMncc .if yield \!|>on i;iiiifall. 



