succession of changes occurs in them after a period of four years, if we observe their minute revolutions; and this applies not only to winds, but to whatever concerns the state of the weather. He begins his lustrum at the rising of the dog-star, in the intercalary year. So far concerning winds in general. CHAP. 49. (48.)—ECNEPHIAS AND TYPHON. And now respecting the sudden gusts[383], which arising from the exhalations of the earth, as has been said above, and falling down again, being in the mean time covered by a thin film of clouds, exist in a variety of forms. By their wandering about, and rushing down like torrents, in the opinion of some persons, they produce thunder and lightning[384]. But if they be urged on with greater force and violence, so as to cause the rupture of a dry cloud, they produce a squall[385], which is named by the Greeks Ecnephias[386]. But, if these are compressed, and rolled up more closely together, and then break without any discharge of fire, i. e. without thunder, they produce a squall, which is named Typhon[387], or an Ecnephias in a state of agitation. It carries along a portion of the cloud which it has broken off, rolling it and turning it round, aggravating its own destruction by the weight of it, and whirling it from place to place. This is very much dreaded by sailors, as it not only breaks their sail-yards, but the vessels themselves, bending them about in various ways. This may be in a slight degree counteracted by sprinkling it with vinegar, when it comes near us, this substance being of a very cold nature[388]. This wind, when it rebounds after the stroke, absorbs and carries up whatever it may have seized on. CHAP. 50.—TORNADOES; BLASTING WINDS; WHIRLWINDS[389], AND OTHER WONDERFUL KINDS OF TEMPESTS. But if it burst from the cavity of a cloud which is more depressed, but less capacious than what produces a squall, and is accompanied by noise, it is called a whirlwind, and throws down everything which is near it. The same, when it is more burning and rages with greater heat, is called a blasting wind[390], scorching and, at the same time, throwing down everything with which it comes in contact. (49.) Typhon never comes from the north, nor have we Ecnephias when it snows, or when there is snow on the ground. If it breaks the clouds, and, at the same time, catches fire or burns, but not until it has left the cloud, it forms a thunder-bolt. It differs from Prester as flame does from fire; the former is diffused in a gust, the latter is condensed with a violent impulse[391]. The whirlwind, when it rebounds, differs from the tornado in the same manner as a loud noise does from a dash.