This Observation was made by Mr. _William Ball_, {153} accompanied by his brother, Dr. _Ball_, _October_ 13. 1665. at six of the Clock, at _Mainhead_ near _Exeter_ in _Devonshire_, with a very good _Telescope_ near 38 foot long, and a double Eye-glass, as the observer himself takes notice, adding, that he never saw that _Planet_ more distinct. The observation is represented by _Figure_ 3. concerning which, the Author saith in his letter to a friend, as follows; This appear'd to me the present figure of _Saturn_, somewhat otherwise, than I expected, thinking it would have been decreasing, but I found it full as ever, and a little hollow above and below. Whereupon the Person, to whom notice was sent hereof, examining this shape, hath by Letters desired the worthy Author of the _Systeme of this Planet_, that he would now attentively consider the present _Figure_ of his _Anses_ or _Ring_, to see whether the appearance be to him, as in this _Figure_, and consequently whether he there meets with nothing, that may make him think, that it is not _one_ body of a Circular Figure, that embraces his _Diske_, but _two_. And to the end that other Curious men, in other places might be engaged, to joyn their Observations with him, to see, whether they can find the like appearance to that, represented here, especially such Notches or Hollownesses, as at A and B, it was thought fit to insert here the newly related Account. * * * * * _A Relation of some _Mercurial_ Observations, and their Results._ Modern _Philosophers_, to avoyd Circumlocutions, call that Instrument, wherein a Cylinder of Quicksilver, of between 28. and 31. Inches in Altitude, is kept suspended after the manner of the _Torricellian_ Experiment, a _Barometer_ or _Baroscope_, first made publick by that Noble Searcher of Nature, Mr. _Boyle_, and imployed by Him and others, to detect all the minut variations in the Pressure and weight of the Air. For the more {154} curious and nice distinguishing of which small changes, Mr. _Hook_ in the _Preface_ to his _Micrography_, has described such an Instrument with a _Wheel_, contrived by himself, and, by these two last years trials of it, constantly found most exact for that purpose: which being so accurate, and not difficult to be made, it were desirable, that those who have a Genius and opportunities of making Observations of this kind, would furnish themselves with such of these Instruments, as were exactly made and adjusted according to the Method, delivered in the newly mentioned place.