Page:The Olive Its Culture in Theory and Practice.djvu/47

Rh growing, first consult the thermometer. A mean temperature of sixty-one degrees Fahrenheit, from the first of March to the end of December inclusive, will be sufficient guarantee; or this same mean, from the beginning of the flowering period—say May twentieth to the end of December—will ripen the berries. Where the summer heat is greater the fruit will ripen earlier.

The olive begins to move in March at a temperature of fifty-two degrees, it buds at fifty-nine degrees and flowers at sixty-seven degrees. The blossoms set at a temperature of seventy-one degrees of heat, and to ripen the fruit a minimum of eighteen thousand five hundred degrees of heat is necessary, dating from the period in March when it first began to move. A good general rule to rely upon would be, that where one can obtain a mean temperature for spring of fifty-six degrees; for summer, of seventy degrees; for autumn, of fifty-eight degrees and in winter a minimum of twenty degrees the olive can always be successfully cultivated; bearing in mind, however, that some varieties require more heat than others and that peculiarities in the atmosphere or the soil may make it impossible to grow the olive even with this temperature. To obtain the mean temperature with the necessary exactitude requires careful observation at least three times a day, and a minimum thermometer to show the lowest temperatures during the night and early morning is imperative. A recent invention, however, has simplified this labor very much; it is known as Drapers' Recording Thermometer, and consists of a dial, driven by clock work, which makes a complete revolution in one week and as it revolves under a pen attached to the thermometer proper a curved line in red ink is drawn on the face of the dial, which shows by lines thereon the exact temperature of the air at every hour during the day and night. The only attention this machine requires is to change the dial once a week, to wind the clock at the same time, and to feed the pen with a few drops of prepared ink. The weekly record dial is then filed away, and thus