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8. The true Magnitude of the Head and Tail of Comets.
TYcho observed the true Diameter of the Comets Head, Anno 1577. to be Three hundred sixty and eight German Miles, and in proportion to the Dia∣meter of the Earth, as 3. to 14. To the Diameter of the Moon, as 1. to 4. and the true length of the Tail at the least 95 Semi-diameters of the Earth, and Eighty one Thousand and seven hundred German Miles.
Longomontanus and Cysatus found the true Dia∣meter of the Head of the Comet in 1618. One hun∣dred and seventy five German Miles, and in propor∣tion to the Diameter of the Earth, as 377. to 3600. the length of the Tail continually variable, and very uncertain; excepting only the 29 of December, on which day it was observed to be 445 Semi-diameters of the Earth, which answers to three hundred eighty two thousand and seven hundred German Miles.