GENERAL CLIMATOLOGY OF THE RAIN-FOREST REGION. 



The following data on the climatology of the Montane Rain-Forest 

 region are based on the records kept at Cinchona, at New Haven Gap, 

 and at Blue Mountain Peak by the Jamaican Department of PubUc 

 Gardens and Plantations, which are the only records ever kept in the 

 higher Blue Mountains. The observations made at these locahties 

 were published currently in the Bulletin of the Botanical Department 

 of Jamaica and in the Jamaica Gazette, but have never been subjected 

 to a systematic analysis. I have secured data for several features 

 (such as the number of rainy days) by a,n inspection of the manuscript 

 records of the Department. 



Using these data as a basis I have endeavored to determine to what 

 extent the physical conditions in certain typical plant habitats depart 

 from the climatic conditions of the region as a whole, and in just what 

 respects the several habitats differ from each other. I obtained records 

 with an air thermograph, a hygrograph, a soil thermograph of the 

 Hallock type, and atmometers of the type devised by Livingston. 

 These results will be presented in the chapter on the relation of physical 

 conditions to habitat distinctions (see p. 41). 



AIR TEMPERATURE. 



The record of air temperatures for Cinchona consists of daily readings 

 of the maximum and minimum and of the current temperatures at 

 7 a. m. and 3 p. m. In view of the constancy of temperature conditions 

 a digest of these records for fifteen years (1891-1905 inclusive) has 

 seemed sufficient to give an accurate set of means and ranges. Owing 

 to the unfortunate custom of making a reading at 3 p. m., it has been 

 necessary to determine the daily mean by taking half the sum of the 

 minimum and the 3 p. m. temperatures.^ In table 1 are exhibited the 

 principal elements of the climate as respects temperature. 



At New Haven Gap a set of observations of the monthly absolute 

 maximum and minimum was taken during the years 1882 to 1893 at a 

 cleared spot in the summit of the Gap at 5,600 feet (1,705 meters) 

 elevation. Diiring the twelve years of these observations there are 26 

 monthly readings missing. A set of observations of absolute monthly 

 maximum and minimum was also taken at Blue Mountain Peak during 

 the years 1890 to 1900, the instruments being exposed upon the cleared 

 summit of the peak at an elevation of 7,428 feet (2,264 meters) . From 

 this record two months are missing. For the sake of comparison I 

 have found by inspection the absolute monthly maximum and mini- 

 mum for Cinchona for the years 1891 to 1900, and table 2 exhibits the 

 means of these data for the three locahties for the years mentioned : 



The absolute maximum for Blue Mountain Peak is 76° in September 

 1891, the absolute minimum 33.3° in February 1893 ; the absolute maxi- 



'Hann, Handbook of Climatology, Transl. by Ward, p. 8. New York, 1903. 

 10 



