Different soils retain heat in proportion to their weight; a pebbly soil retains heat longer than one of fine sand. Chalky and clay soils quickly lose heat; and, on this account, the former is called an early soil, and the latter a late one. The color of the soil has much to do with the absorbtion of heat. In any given earth there is a difference of fourteen degrees, Fahrenheit, between the extremes of color.
The ancients thought that the olive would not grow unless it had the sea air, and laid down the rule, that it should not be planted more than ninety miles inland. The Arabic and Latin authors follow the same recommendation; but it has been well established, that the olive can be grown at any distance inland, provided the soil and climate are agreeable to it. Pliny remarks, the olive of the low land is more liable to disease, than that grown on high ground.
