The average crop divided by the average rainfall of the preceding year shows that each inch of rain corresponds to about 800 hogsheads in the resulting crop; the extreme limits of variations are 713 and 877 hogsheads, so that in general Governor Rawson proposes to predict the crop that will be gathered during the dry season, February to May, each year by simply multiplying the rainfall of the preceding calendar year by 800. The average uncertainties of the crop thus predicted is very small, the extreme error being 28 per cent positive following the wet year 1861 and 4 per cent negative for a certain dry year; therefore as an improvement on this method he adopts the rule of adding 7 per cent for wet years and subtracting 7 per cent for dry years, the average year being that which corresponds to 55 inches of rainfall.

In supplementary calculations Rawson and Walcott show the chances of a good crop as calculated from a large, small, or average rainfall, respectively, for each month of the year, but I do not find that they have at any time compared the crop with the total rainfall for the whole eighteen months or growing period that immediately preceded the crop, which comparison I have therefore made and give in Table III.

From all which it appears that large rains gives large crops, but occasionally much smaller rains do also, so that it may reasonably be suspected that here, as elsewhere, the sunshine must be considered; probably large rains are only of advantage when they occur at such a time that they do not diminish the sunshine and in such a manner that they do not wash the soil too severely.

It would have been desirable to have stated these crops as yields. per acre rather than as total crops, but I find no statement of the actual acreage in cane. Rawson gives only the total areas of the six divisions of the island, which sum up 107,000 acres; probably two-thirds of this is planted in sugar cane, so that an inch of annual rainfall corresponds to 800 or one-ninetieth of a hogshead of sugar per acre.

700009

It is, however, more proper to reason upon this matter as follows: Eleven poor crops gave, according to Table I, an average deficit of 15 per cent; 12 good crops gave an average excess of 14 per cent; the average rainfalls were 55.15 and 58.18, respectively. Therefore an increase of 1 inch in rainfall corresponds to a gain of 3, or 10 per cent of an average crop.

TABLE I.-Barbados sugar crop and monthly rainfall.

Year.

Excess of sugar crop.

Jan. Feb. Mar. Apr.

May. June. July.

Per cent. Inches. Inches. Inches. Inches. Inches. Inches. Inches.

TABLE I.—Barbados sugar crop and monthly rainfall-Continued.

TABLE II.-Barbados sugar crop and rainfall of the growing period.

TABLE III.-Barbados sugar crop and rainfall of preceding year.

NOTE. In calculating the average crop and the respective annual excesses or deficits given in Tables I and III Governor Rawson says that "he has made an arbitrary division of the whole period into two sections marked by the introduction of the use of guano as a fertilizer." For the first section, 1847-1856, inclusive, he considers 38,795 hogsheads as the average, but for the second section, 1857-1872, inclusive, he takes 45,036 hogsheads as the average. He states that this is virtually assuming that during the whole period climatic and other conditions were nearly constant and that the principal difference was in the introduction of the use of guano and the great increase of crops was due to that.' During the first interval an inch of rain corresponded to 642 hogsheads of sugar in the crop of the next year, but during the second interval it corresponded to 800 hogsheads.