(3.) The olive is composed of a stone, oil, flesh, and amurca:[1652] the last being a bitter liquid, principally composed of water; hence it is that in seasons of drought it is less plentiful, and more abundant when rains[1653] have prevailed. The oil is a juice peculiar to the olive, a fact more particularly stated in reference to its unripe state, as we have already mentioned when speaking of omphacium.[1654] This oil continues on the increase up to the rising of Arcturus,[1655] or in other words, the sixteenth day before the calends of October;[1656] after which the increase is in the stone and the flesh. When drought has been followed by abundant rains, the oil is spoilt, and turns to amurca. It is the colour of this amurca that makes the olive turn black; hence, when the berry is just beginning to turn that colour, there is but little amurca in it, and before that period none at all. It is an error then, on the part of persons, to suppose that that is the commencement of maturity, which is in reality only the near approach of corruption. A second error, too, is the supposition that the oil increases proportionally to the flesh of the berry, it being the fact that the oil is all the time undergoing a change into flesh, and the stone is growing larger and larger within. It is for this reason more particularly, that care is taken to water the tree at this period; the real result of all this care and attention, as well as of the fall of copious rains, being, that the oil in reality is absorbed as the berry increases in size, unless fine dry weather should happen to set in, which naturally tends to contract the volume of the fruit. According to Theophrastus,[1657] heat is the sole primary cause of the oleaginous principle; for which reason it is, that in the presses,[1658] and in the cellars even, great fires are lighted to improve the quality of the oil.