CANE SUGAR. 



A very sweet and pure cane is found in those districts where the average 

 temperature is such that a longer period is taken to maturity, and where 

 a season cold enough to check the growth of the cane occurs ; when this 

 arrest of growth happens, the energy of the cane is presumably directed 

 towards the elaboration of the material already formed, rather than to the 

 formation of new substance; it is in the districts lying on the confines of 

 the tropics that this phenomenon happens. 



Rainfall. The amount of water essential to the best growth of the 

 cane is discussed in the chapter on irrigation. Under natural conditions an 

 excessive rainfall results in a cane of low sugar content, a deficiency in 

 rainfall resulting in a cane with much fibre. The optimum rainfall is, 

 of course, directly correlated to the prevailing temperature, the soil evapora- 

 tion increasing with rise in temperature ; thus Stubbs, 6 referring to Louisiana 

 conditions, gives an annual rainfall of about 60 inches as most advantageous, 

 of which about 45 inches should fall in the wet or growing season, and about 

 .15 inches during the dry. Such an annual rainfall would be classed as a 

 severe drought in Demerara, where a precipitation of about 100 inches 

 results in the maximum crop ; the rainy season there should commence in mid 

 December, and continue without prolonged intervals of drought to the end of 

 July, the earlier months of the year being dry enough to allow of the 

 cultivation of the heavy clay soils. A heavy rain immediately before harvest 

 is reflected in a diluted juice, the vessels which carry plant food being then 

 full of water at the moment of cutting. 



Wind. The chief effect of winds in regard to agriculture, whether of 

 the cane or otherwise, is concerned with the removal of soil moisture ; the 

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

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

 is of influence in this connection ; a wind blowing from the sea to the land 

 conveys air heavily charged with moisture, increasing the humidity of the 

 atmosphere, and lessening the tendency to soil evaporation ; it is probably for 

 this reason that in Demerara surface evaporation from exposed shallow vessels 

 is small compared with what would be expected from temperature conditions 

 alone. The surface evaporation there is 35*12 inches, per annum, compared 

 with 31-04 inches at Oxford, and 82-28 inches at Bombay. 7 In Demerara the 

 prevailing winds are the North-east Trades, blowing directly from the Atlantic, 

 with no intervening mountains to cause a deposit of water as rain. Maxwell 8 

 in Hawaii found that 120 square inches of exposed area evaporated in 270 days 

 33,480 grams, of water, the relative humidity being 79'5, and the average 

 temperature 79-5 ; this is equivalent to an evaporation of 28-4 inches per 

 annum. Under equal conditions, but with the water protected from the wind, 



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