Page:Philosophical Transactions - Volume 001.djvu/256

 the second Face of Mars, he could not see it the 14. and 16. of April.

From all which Observations he Judges it to be evident, that the Period of this Planets Revolution is not perform'd in the space of 12. hours 20. minutes, but in about 24. hours 40 minutes; more exactly to be determin'd by comparing distant Observations: And that those who affirm the former, must have been deceived by not well distinguishing the two Faces, but that having seen the second, taken it for the first.

All which he concludes with this Advertisement, that, when he defines the time of the Revolution of Mars, he does not speak of its Mean Revolution, but onely of that, which he observ'd, whilst Mars was opposite to the Sun; which is the shortest of all.



K. One of the Faces of Mars, as S. Cassini observed it March 3. (st.n) 1666 in the Evening, with a Glass of 24 Palmes.

L. The other Face, as he saw it Febr. in ththe [sic] Evening.

M. The first Face, as S. Campani saw at Rome, March 3. 1666, in the Evening, with a Glass of 50 Palmes.

N. The second Face, as the same Campani observ'd it March in the Evening.

O. The Figure of Mars, as it was seen at Rome by a Telescope of Divini of 45 Palmes, March.

P. The Figure of the said Planet, as it was seen the same day and hour at Bononia by Cassini; being that of the second Face.

These, as they were made, so they were imparted, by Mr. Hook, as follows:

A. 1666. June 26. between 3. and 4. of the Clock in the morning, I observed the Body of Jupiter through a 60. foot glass, and found the apparent Diameter of it through the Tube, to be somewhat more than 2. degrees, that is, about four Rh