This important Difference between two very Learned, and very deserving Persons, being come to the knowledge of some of the ablest _Philosophers_ & _Astronomers_ of _England_, hath been by them thought worthy their Examination: and they being at this very present employed in the discussion thereof, by comparing what hath been done and published by the Dissenters, and by confronting with them their own Domestick Observations, are very likely to discern where the mistake lies; and having discern'd it, will certainly be found hightly impartial and ingenuous in giving their sense of the same. {109} * * * * * _Of the _Mundus Subterraneus_ of _Athanasius Kircher_._ This long expected _Subterraneous World_, is now come to light, dedicated (at least the _Exemplar_, that hath been perused by the _Publisher_ of these _Papers_, who hears, That other _Copies_ bear Dedication to other _Great Princes_) both to the present Pope, as being esteemed by the author to have a part of his _Apostolical Kingdom_ there; and to the _Roman Emperor_ now Regent, who indeed in his Kingdom of _Hungary_, and in several Provinces of _Germany_, hath very many and very considerable things, worthy to be observed, under _Ground_. To give the Curious a taste of the _Contents_ of this _Volume_, and thereby to excite them to a farther search into the recesses of Nature, for the composure of a good _Natural History_; they may first take notice, That the Author, having given an account in the _Preface_, what encouragement he received, for writing this Book, from the opportunity of Travelling with the _Cardinal_ of _Hassia_ into _Sicily_ (in which Voyage, he saith, He met with, as it were, an _Epitome_ of what may be observable in the Subterraneous parts of the Earth; and in particular, with an Earth-quake of 14 daies duration, very instructive to him concerning several great Secrets of Nature:) having I say, thus Prefaced, he divided his Work into 12 _Books_, wherein he affirms not only to have explicated the Divine Structure of the under-ground World, and the wondrous distribution of the Work-houses of Nature, and her Majesty and Riches therein; but also to have opened the Causes of her Effects and Productions; whence, by the Marriage of Nature and Art, a happy Issue may follow for the use and benefit of Humane Life. In the _First_ Book, he considers the nature of the Centre of the Earth, where he delivers several _Paradoxes_ touching the same, and Discourses of the Motion of heavy Bodies, of Pendulems, of Projectils. {110}