He concludeth with two _Celestial Observations_; whereof the _one_ imports, what multitudes of Stars are discoverable by the _Telescope_, and the variety of their magnitudes; intimating with all, that the longer the Glasses are, and the bigger apertures they will indure, the more fit they are for these discoveries: the _other_ affords a description of a _Vale_ in the _Moon_, compared with that of _Hevelius_ and _Ricciolo_; where the Reader will find several curious and pleasant Annotations, about the Pits of the _Moon_, and the Hills and Coverings of the same; as also about the variations in the _Moon_, and its _gravitating_ principle, together with the use, that may be made of this Instance of a gravity in the _Moon_. As to the _Inventions of Art_, described in this Book, the curious Reader will there find these following: 1. A _Baroscope_, or an Instrument to shew all the Minute Variations in the _Pressure of the Air_; by which he affirms, that he finds, that before and during the time of rainy weather, the Pressure of the Air is less; and in dry weather, but especially when an _Easterly_ Wind (which having past over vast Tracts of Land, is heavy with earthy particles) blows, it is much more, though these changes be varied according to very odd Laws. 2. A _Hygroscope_, or an Instrument, whereby the _Watery steams_, volatile in the Air, are discerned, which the Nose it self is not able to find. Which is by him fully described in the Observation touching the _Beard of a wild Oate_, by the means whereof this Instrument is contrived. 3. An Instrument for _graduating Thermometers_, to make them _Standards_ of _Heat_ and _Cold_. 4. A _New Engine_ for _Grinding Optick Glasses_, by means of which he hopes, that any Spherical Glasses, of what length {32} soever, may be speedily made: which seems to him most easie, because, if it succeeds, with one and the same Tool may be ground an _Object Glass_ of any length or breadth requisite, and that with very little or no trouble in fitting the _Engine_, and without much skill in the _Grinder_. He thinks it very exact, because to the very last stroke the Glass does regulate and rectifie the _Tool_ to its exact Figure; and the longer or more the _Tool_ and _Glass_ are wrought together, the more exact will both of them be of the desired Figure. He affirms further, that the motions of the Glass and Tool do so cross each other, that there is not one point of eithers surface, but hath thousands of cross motions thwarting it, so that there can be no kind of _Rings_ or _Gutters_ made, either in the _Tool_ or _Glass_.