30 M E M O I R S g/" /^^r 
approaching him on one fide more than the other; and if this 
ring were turned round on one of its diameters, it would then 
delcribe fuch a concave fphere, as the external one of the earth is 
fuppolcd to be ^ and fince the ring, in any given pofition, would 
in the fame manner retain the centre of Saturn in its own, it 
follows, that fuch a concave fphere may move with another 
included in it, having the lame common, centre j nor can it well 
be fuppofed otherwife, confidering the nature of gravity 5 for 
ihould thefe globes be adjufted once to the fame common centre, 
the gravity of the parts of the concave would prefs equally to- 
wards the centre of the internal ball, which equality mull ne- 
ceffarily continue till Ibme external force difturbs it, which is not 
eafy to imagine in our cafe j this perhaps might more intelligibly 
be expreffed, by faying that the inner globe, being pofited in the 
centre of the exterior, mufl neceflarily alcend, which way foever 
it move 5 that is, it muft overcome the force of gravity prefling 
towards the common centre, by an impulle it muft receive from 
fome external agent; but all outward efforts being fufficiently 
fenced againft by the furrounding fhell, it follows, that this 
Nucleus, being once fixed in the common centre, muft always 
remain there : As to the leaking of the water thro* this Ihell, 
when there is once a pafTage for it to run thro\ is an objection 
feemingly of weight 3 but when we confider, how tightly great 
beds oi chalk or clay, and much more ftone, do hold water, and 
even caves arched with fand, no man can doubt but the wifdom 
of the creator hath provided for the macrocofm, by many other 
ways than can be imagined or expreffed, efpecially fince we iee 
the admu'able and innumerable contrivances, wherewith each 
meaneft individual is furniflied, both for its own defence, and 
the propagation of its fpecies ^ what curiofity in the ftru^ture, 
what accuracy in the mixture and compofition of the parts ought 
we not to expert in the fabric of this globe, defigned for the laft- 
ing habitation of lo many various fpecies of animals, in each of 
which there want not many inftances, that manifeft the boundleis 
power and goodncfs of their divine author? And can we then 
think it a hard luppofition, that the internal parts of this earth 
fhould be replete with fuch faline and vitriolic particles as may 
contribute to petrifaction, and difpofe the traniuding water to 
ilioot and coagulate into ftone, lb as continually to fortify, and if 
need Vv'ere, to confolidate any breach or flaw in the concave 
furface of the fnell ? And this perhaps may, not without reafon, 
be luppofed to be the final caufe of the admixture of the magneti- 
cal matter in the mafs of the tcn-eftrial parts of our globe j viz. to 
ftrengthen 
