And though I desired to make Observations, about 3. of the Clock those mornings; yet something or other interven'd, that hindred me, till _March_ 28. about 3 of the Clock, the Air being light (in weight) though moist and a little hazy; when I plainly saw it, to have the form, represented in I; which is not reconcileable with the other Appearances, unless we allow a _Turbinated_ motion of _Mars_ upon its Center: Which, if such there be, from the Observations made _March_ 21. 22. and 23. we may guess it to be once or twice in about 24. hours unless it may have some kind of _Librating_ motion; which seems not so likely. Now, whether certainly so or not, I shall endeavour, as oft as I have opportunity, further to observe. [Illustration] A particular direction to the _Figures_ mentioned in the precedent discourse. A. _March _3^{d.} 00^{h.} 20^{m.}_ in the morning: the Air having many {242} inflecting parts dispersed up and down in it; by the _Wheel Barometer_, heavy,_ B. _Another Scheme, which I drew from my Observation, about 10. minutes after, the same morning. Both these were observed with a very deep Eye-glass._ C. _March_ 10^{d.} 00^{h.} 20^{m.} _in the morning: the Air heavy and inflective. Use was made of a shallow or ordinary Charge._ D. _March_ 10^{d.} 3^{h.} 00^m _in the Morning; the Air very heavy and Inflective, which made it glare and radiate, and be more confused, than about 3. hours before. A shallow Charge._ E. _March_ 21^{d.} 91/2^{h.} _post merid; the Air light (in weight) and clear, without inflecting parts; the Face appear'd most distinctly of this Forme. A shallow Charge._ F. _March_ 21^{d.} 113/4^{h.} _post merid; the Air continuing very light and clear, without inflecting vapours. A shallow Charge._ G. _March_ 22^{d.} 81/2^{h.} _post mer. the Air clear, with few inflecting veins in it, and indifferent light. A shallow Charge._ H. _March_ 23^{d.} 91/2^{h.} _post mer. the Air pretty light, but moist, and somewhat thick and hazy, but seem'd to have but few veins, or inflecting parts._ I. _March_ 28^{d.} 3^{h.} _p. m. much the same kind of Air with that of March 23; light, moist, and a little hazy, with some very few veins._ * * * * * _Observations made in _Italy_, confirming the former, and withall fixing the _Period_ of the Revolution of _Mars_._ These Observations we shall summarily present the Curious in these parts with, as they were lately presented (by Letter from his Excellency the Ambassadour of _Venice_, now residing at the Court of _France_) to the _Royal Society_, in some printed sheets of Paper, entituled, _MARTIS, circa Axem proprium Revolubilis, Observationes, BONONIAE a JO. DOMINICO CASSINO habitae;_ come to hand _June_ 3. 1666. In these Papers the Excellent _Cassini_ affirms;