32 MEMOIRS of the 
can we, without rafhnels, unbecoming philofophers, adventure to 
?.{Iert the impoflibility of peculiar luminaries below, of which we 
have no manner of idea. 
For the firther explication of this fubject, the following fcheme 
is fubjoincd, wherein, Fig. i. Plate II. the earth is reprelented 
by the external circle, and the three internal circles arc made 
nearly proportionable to the magnitudes of the planets Venus^ 
Mcirs^ and Mercury^ all which may be included within the globe 
of the earth, and all the arches be more than fufficiently ftrong to 
bear their weighty the concavity of each arch, which is /haded 
differently from the reft, is fuppofed to be made up of magnetical 
matter, and the whole to turn about the fame common ^xispp^ 
only with this difference, that the outer fphere ftill moves fome- 
what failer than the inner 5 thus, the diameter of the earth being 
about 8coo Englijh miles, Mr. Halley allows 500 miles for the 
thickneis of its ihell, and another fpace of 500 miles for an inter- 
veening medium, capable of an immenle atmofphere for the ule 
of the globe of Venus '■, to Venus, again he allows a (hell of the 
fame thickneis, and he leaves as great a fpace between her conca- 
vity and Mars--:, ib likewife from Mars to Mercury^ which latter 
ball he fuppoles folid, and about 2OCO miles in diameter: A 
farther ule of this cavity of the earth, may be to diminifh the 
fpecific gravity thereof in refped of the moon ^ for the oppofition 
of the yEr/75;', to the motions of the planets, in a long time 
becomes lenlible, and coniequently the greater body mufl: receive 
a lefs oppolition than the Imaller, unlefs the fpecific gravity of the 
leiler doth proportionably exceed that of the greater, in which cafe 
only they can move together 5 fb that the cavity in the earth may 
well ferve to adjuft its weight to that of the moon 5 for otherwile 
the earth would leave the moon behind it, and Ihe become ano- 
ther primary planet. 
7*he Trocefsof making the Phofphorus; by Mr. Boyle. Phil. 
Trani: N^ig^T. p. 583. 
THERE was taken a confidcrable quantity of human urine, 
becaufe it yields but a fmall proportion of the deiired 
quinteffcnce, and a good part of it at Icaft, had been digefted for 
a pretty while, before it was uled j then this liquor was diftillcd 
witli a moderate heat, till the fpirituous and faline parts were 
drawn off; after which, the fupcrfluous moifture was alio eva- 
porated, till the remaining fubft.mcc was brought to the confiftence 
c)f a Ibmewhat thick fyrnp, or a thin cxtr?6l; this done, it was 
wt'll incorporated with thrice its weight of iine white fand^ and 
the 
