are. The first comet presented in the illustration is called *disceus*, because it reflects the shape of a disk or a shield. The second is *kometes*, which is to say "hairy" or "long-haired"; this name is particularly appropriate, as most comets appear in this form. The third is *keratias*, or "horned." The fourth is called *pogonias*, the "bearded" comet. The fifth is *akontias*, having the form of a javelin. The sixth is *xiphias*, or sword-shaped. The seventh is *pithos*, representing the likeness of a jar—a type that some later called a "solar" comet or a "rose." The eighth is *hippeus*, a word which usually denotes a horseman among the Greeks, but which Pliny applies to this comet as if calling it "equine." The ninth and last is called *lampadias*, because it represents the likeness of a burning torch. These species of comets are depicted in Illustration II.

However, Arabic authors assigned various names to comets based on both their appearance and their perceived powers. We have judged it unnecessary to bring all of these into the discussion, as there is not such a great discrepancy among the drawn figures that the various comets cannot be reduced to a single class, such as the shield-shaped and solar comets. Furthermore, other distinctions among comets can be categorized by their shapes: there are comets that resemble a trumpet or a comb, some that are quadrangular, and even some adorned with two or three horns. Nevertheless, Cornelius Gemma strongly doubts the reality of these shapes, particularly those mentioned by the Arabs; he argues that no records from the ancients mention comets shining upon the world other than those representing the likeness of a javelin, a sword, or a pyramid. They mention a horned comet only once.

Moreover, if any other image of a comet is found named and described by them beyond those mentioned, one must wonder whether the ancients confused other fiery meteors with legitimate and genuine comets. Aristotle, therefore, acted more correctly and satisfactorily by reducing all the varieties of shapes to just two types when reviewing comets: namely, the *kometes* and the *pogonias*, depending on whether their "hair" extends in length or in width. For this reason, the common people today call comets "hairy," "bearded," or "tailed," although some seem to project their particular radiance in a sharp figure and others in a broad one.

So that nothing is missing from our history, we have decided to present other differences among comets based on their shape in Illustration III. Here, the first species is called *keratias*, the "horned" type, although it appears to some extent to take the form of a trumpet. The second is a different *xiphias*, or sword-shaped comet. The third is yet another *xiphias*. The fourth is *tetragonias*, or "square." The fifth and seventh are called various *hippeus* types, because they resemble a horse in different ways. Alternatively, we might follow Albertus Magnus, who established five differences of comets, not based on the wandering stars (namely Mercury, Venus, Jupiter, Mars, and Saturn), but according to five differences in their material vapor. For although all cometary vapor is generally thick and cohesive, it can be thick, thin, or intermediate depending on the nature of the material. From these, three intermediate states result, and consequently, there are only five differences among comets based on their matter.

We must not omit two figures of comets that Cornelius Gemma proposed for consideration, which he called "Saturnian" comets, named either after the star or because of their color. One of these shone in the year of our Lord 1558, on the seventeenth day of August, at sunset, around the twelfth degree of Virgo; it was separated from the tail of the Great Bear by a distance of twenty-eight degrees. It stood in the west with a sad and mournful face—clearly of a Saturnian nature—and stretched its tail toward the eastern region. However, it was not seen for long, for as rain came on, it vanished before the seventh day.

Gemma likewise mentions another comet of a Saturnian nature, which shone in the year of human salvation 1569, around the beginning of November. It had a very long tail extending toward the east. Around the twentieth day of the same month, it was seen a little higher, but shortly thereafter, as the force of the winds grew stronger and the rain became continuous, it was dissolved. The images of these are seen in Illustration IV.