He wishes, that all the changes that shall fall out in this Comet, might be exactly observ'd; because of its not being swift, and the Motion of the Earth very sensible, unless the Comet be extreamly remote, we should find much more light from this, than the former Star, about the Grand Question, whether the Earth moves or not; this Author having all along entertained himself with the hopes, that the Motion of Comets would evince, whether the Earth did move or not; and this very Comet seemed to him to have by design appeared for that end, if it had had more Latitude, and that consequently we might have seen it before Day break. He wishes also, that, if possible, it may be accurately observed, whether it will not a little decline from its great Circle towards the South; Judging, that some important truth may be thence deduced, as well as if its motion retarded more, than the place of its Perigee (which will be more exactly known when all the passed Observations shall have been obtained) and its greatest Motion do require.
He fears only, that it being then to rise at Break of Day, exact Observations cannot be made of it: but he would, at least have it sought with Telescopes, his Ephemerides directing whereabout it is to be.
April 10. it was to be over against the point of the Triangle, and from thence more Southerly by more than two degrees; and April 11. over against the bright Star of Aries, April 17. over against the Stars of the Fly, a little more Southerly, and May 4 it is to be over against the Pleiades, and about the fourth or fifth of the same Month, it is to be once more in Conjunction with the Sun; after which time, the Sun will move from it Eastward, and leave it towards the West; which will enable us to see it again at a better hour, provided the cleerness of the Day-break be no impediment to us. He addeth, that this Star must have been the third time in Conjunction with the Sun, about the time when it first began to appear: and foresees, that from all these particulars many considerable consequences may be deduced.
It will cut the Ecliptick about the end of July, new Style, a little more Eastwards than the Eye of Taurus; at which time there will be no seeing of it, except it be with a Telescope.
It will be towards the End of April, new style, twice as far distant as it was in Perigee, thrice as far, May the fourth, four times, May the eighteenth, and five times, June the first, &c.
He would not have Men surprised, that there have been two Comets within so short a time; seeing, saith he, there were four, at least three, in the Year 1618. and in other Years there have been two and more at the same time. What he adds about their signification, we leave to Astrologers to dispute it with him. He concludeth with asking pardon, if he have committed mistakes, which he hopeth he shall obtain the sooner, because of the small time he hath had for these calculations; and he wishes that he could have made all the Observations himself, seeing that it is easie to fail, when one must trust to the Observations of others, whereof we know not the exactness: where he instanceth, that according to his Observations, the way of the Comet should go neerer the Ecliptick than he hath marked it, even without having any great regard to the Refractions: but since he would subject himself to others, he hath made it pass a little higher, which, he saith, was almost insensibly so, in those few days that he was observing and writing, but that this may perhaps become sensible hereafter; which if it be so, he affirms that it will cut the Ecliptick and Equator sooner, than he hath marked it, &c. However, he thinks it convenient, to have given aforehand a common Notion of what will become of a Comet, to prepare men for all the Changes that may fall out concerning it: which he affirms he hath endeavoured to do; the rest being easie to correct, as soon as any good Observations, somewhat distant, have been obtained, considering, that there need but two very exact ones, a little distant when the Star is not swift, to trace its Way; although there must be at least three, to find out all the rest. But, then would he have it considered, that although his Method should be very exact, if there be not at hand Instruments big enough, and Globes good enough to trust to, nothing can be done perfectly in these kind of Predictions.