710 FRUIT CULTURE IN FOREIGN COUNTRIES. 



Giving 5t mean temperature of 19.7, which, multiplied by 138 sums up 

 to 2,718, less by about 700 than is required for maturing even the 

 earliest variety of the fruit. 



Altitude, in as far as it brings about a decrease of the temperature, 

 is equivalent to latitude, and it is admitted that each 181 meters of 

 height represent a change of climate equivalent to 1 of latitude, from 

 which the conclusion may be drawn that olive culture can be carried 

 on at high altitudes only in the southern parts of its habitat, and vice 

 versa. In the vicinity of Madrid there are productive groves stand- 

 ing on ground that has 655 meters of elevation above sea-level. The 

 altitude being 40 24' 30", and 615 meters being equivalent to 3 24', 

 the climatic conditions are those of latitude 53 48' 30". In the prov- 

 ince of Granada trees are found at an altitude of 1,000 meters above 

 sea-level, representing 5 31' 30", which added to the latitude of the 

 district, which is 37 II 7 10", brings up the effective latitude to 42 

 42' 40". 



Exposure and incline are most important factors in olive culture. 

 Exposure varies in its effects, both according to latitude and to local cir- 

 cumstances, hence no invariable rule can be given, though generally 

 southern exposure is best, as being less liable to frost. In a warm, 

 dry climate, however, trees thus placed will need irrigation in order to 

 do well. Near the northern limits of the olive region, and on high 

 ground, where frosty nights are common in the fall, eastern exposure 

 is deprecated, because in such situations the first rays of the sun bring 

 about very sudden and abrupt changes of temperature. A quick thaw 

 after a moderate frost will generally cause more injury than a period of 

 more severe cold followed by gradual thawing; this accounts for the 

 fact that after a spell of very hard cold the trees most injured are tho.se 

 most accessible to the rays of the sun. 



As regards incline, it is held by most growers that slightly rising 

 ground is preferable to a perfect level. The benefit from an inclined 

 situation, with southern exposure, increases as one goes further north, 

 as the obliquity of the sun's rays is thereby counteracted. The rise 

 should, however, not exceed the ratio of 6 meters to 100, as on steeper 

 ground cultivation by plowing becomes difficult and the soil covering 

 the roots on the upper side of the tree is apt to wash away. At inclines 

 much exceeding the above it is usually necessary to bank up ttte ground, 

 thus creating a succession of small level terraces, involving much labor 

 and expense, and also losing the advantage derived from the greater 

 perpendicularity of the suu's rays upon inclined surfaces. 



Natural or artificial obstacles to injurious winds, such as mountains, 

 forests, or walls, shelter a certain extent of ground on their lee side. 

 Spots sheltered on the north are usually considered as being benefited 

 thereby to the extent of fully one degree of latitude. The ground shel- 

 tered extends horizontally in the ratio of 11 to 1, as compared to the 

 height of the obstacle ; thus, a mountain chain 1,000 meters high will 



