28 CHAPTER III 



in part for the low percentage of sugar in canes grown in the equatorial 

 rainbelt. 



The remaining climatic factor to be considered is that of the winds, the 

 chief effect of which is concerned with the removal of soil water. The 

 more frequently the stratum of air over the soil is removed the greater is 

 the evaporation. The point of the compass from which the wind blows is 

 also of consequence. When the wind blows from the sea to the land air 

 heavily laden with moisture is conveyed thereto, whereby the soil evaporation 

 is lessened. It is probably for this reason that the surface evaporation 

 from shallow exposed vessels is smaller in Demerara than would be expected 

 from temperature conditions alone. Here it reaches 35*21 inches per annum, 

 compared with 31*04 at Oxford and 88-28 at Bombay. 22 In Demerara the 

 prevailing winds are the north-east trades blowing from the Atlantic Ocean, 

 with no mountains to intervene and cause a deposit of the air-borne 

 water as rain. Maxwell 23 in Hawaii found that 120 sq. ins. of exposed 

 area evaporated in 270 days 33,480 grams of water, the relative humidity 

 being 79-5, and the average temperature 79*5 F. Under equal conditions, 

 but with the water protected from the wind, the evaporation was equal to 

 12' i inches per annum. To a certain extent the evil effects of winds may be 

 mitigated by the judicious planting of windbreaks. 



Crop and Planting Time. The combined influence of rainfall and tem- 

 perature determines the harvest and planting seasons. The harvest takes 

 place in the dry season, and mainly after the cane has reached maturity. 

 In those localities that have a cool season, the harvest time is coincident 

 therewith, and its duration is limited by the commencement of the rains, 

 which not only mark the beginning of the period of vegetative activity, 

 but also render haulage operations impossible. Conversely, the rainy season 

 is selected for planting, and the amount of rain falling in a period also 

 determines the possibility or not of ploughing operations. The harvest 

 time of the principal cane-growing districts is as follows : 



Cuba and the West Indies December or January to June. 



Java May to November. 



Mauritius and Reunion August to December. 



Louisiana October to January. 



Hawaiian Islands December to September. 



Peru October to February. 



Brazil- October to February. 



Argentina June to October. 



Egypt December to March. 



Queensland June to November. 



Mexico December to May. 



Philippines December to March. 



British India January to April. 



Spain March to May. 



Formosa January to May. 



Fiji June to November. 



Madeira February to May. 



Natal and Portuguese East Africa May to November. 



British Guiana has two and sometimes three crop seasons ; the main 

 harvest is from September to December, with a short season in May 

 and June and an occasional one in March. 



