Now therefore, to the end, that the Looser may have his benefit by it, as well as the Gainer, it would not be amiss, that the condition were made thus, that the latter should grant the moity of his gain to the Proposer; that thereby he might be enabled to bring to light both those, and some other useful inventions, for the Service of Mankind. And to manifest, that it is not for his own interest only, that the _Proposer_ mentions this; he is willing to impart from that moity, so received, the full moity again to any other person within his Majesty's Dominions, who shall first of all give notice of his Undertaking to prove or disprove the said Identity, and perform it accordingly within the space of two Months, to be computed from the present Date. Those that have a mind to engage, may repair to the Printers of these _Tracts_, where they may know further. [Illustration] * * * * * _A new Contrivance of _Wheel-Barometer_, much more easy to be prepared, than that, which is described in the _Micrography_; imparted by the Author of that Book._ This is only an easy way of applying an _Index_ to any _Common Barascope_, whether the Glass be only a Single Cane, or have a round Bolthead at the top. And by the means thereof, the {219} Variation of the Altitude of the _Mercurial_ Cylinder, which at most is hardly three Inches, may be made as distinguishable, as if it were three Foot, or three Yards, or as much more, as is desired. The manner hereof is visible enough by _Figure_ I: where A B C represents the Tube, which may be either Blunt, or with a Head, as A B C (by which latter shape, more room is allow'd for any remainder of Air, to expand the better.) This is to be filled with Quick-silver, and inverted as commonly; but into a Vessel of Stagnant Mercury, made after the fashion of I K, that is, having its sides about 3 or 4 inches high, and the Cavity of it equally big both above and below; and if it can be (besides that part, which is fill'd by the end of the _Mercurial_ Tube, that stands in it) of equal capacity with the hollow of the Cane about B: For then the Quicksilver rising as much in the hollow of I, as it descends at B, the difference of the height in the Receiver I, will be just half the usual difference, And if the receiving Vessel I K have a bigger Cavity, the difference will be less, but if less, the difference will be greater: But, whether the difference be hereby made bigger or less, 'tis no great matter, since by the contrivance of the _Wheel_ and _Index_ (which is more fully described in the _Preface_ to the _Micrography_) the least variation may be made as sensible as is desired, by diminishing the bigness of the Cylinder E, and lengthening the _Index_ F G, according to the Proportion requisite. * * * * * _An Account of _Four Suns_, which very lately appear'd in _France_, and of two _Raine-bows_, unusually posited, seen in the same Kingdom, somewhat longer agoe._