478 PHILOSOPHICAL TRANSACTIONS. [anNO 1 692-3. 



Venus again I give a shell of the same thickness, and leave as great a space 

 between her concave and Mars ; so likewise from Mars to Mercury, which 

 latter ball we will suppose solid, and about 2000 miles diameter. 



Since this was written, a discovery I have made in the celestial motions, seems 

 to render a farther account of the use of the cavity of the earth, viz. To 

 diminish its specific gravity in respect of the moon : for I think I can demon- 

 strate, that the opposition of the ether to the motions of the planets, in long 

 time becomes sensible ; and consequently the greater body must receive a less 

 opposition than the smaller, unless the specific gravity of the smaller do pro- 

 portionably exceed that of the greater, in which case only they can move to- 

 gether ; so that the cavity I assign in the earth may well serve to adjust its 

 weight to that of the moon; for otherwise the earth would leave the moon 

 behind it, and she become another primary planet. 



A Paper of the Hon. Robert Boyle, deposited with the Secretaries of the Roj/al 

 Society, Oct. 14, ] 680, and opened since his Death; being an Account of his 

 making Phosphorus, ^c* N° I96, p. 583. 



Sept. 30, 168O, there was taken a considerable quantity of human urine, 

 because it yields but a small proportion of the desired quintescence, and a 

 good part of this at least had been digested for a pretty while, before it was 



* At p. 489, Vol. II. of this abridgment, it has been mentioned in the biographical anecdotes 

 concerning Kunckel, that Mr. Boyle deposited with the secretaries of the Royal Society, some years 

 before his death, an account of a process, whereby he succeeded in procuring phosphorus from 

 urine. This he did at a time (168O) when the processes of Brandt and Kunckel were not known, 

 or if known were kept a profound secret. It is true that Mr. Boyle had previously seen some spe- 

 cimens of phosphorus, both solid and liquid, which had been brought to England by Kraaft ; but 

 this person was ignorant of chemistry ; and all that Mr. Boyle could collect from him was, thai the 

 phosphorus which he exhibited was produced from " somewhat that belonged to the human body." 

 Mr. Boyle therefore appears to be entitled to the claim of having discovered a method of obtaining 

 this curious product, equally with the German chemists, Brandt and Kunckel. Nor is this claim by 

 any means invalidated by the circumstance meniioned by Stahl, viz. that Kraaft told him he had 

 communicated the process to Mr. Boyle ; as Kraaffs general character, and in particular his treacherous 

 conduct towards Kunckel, destroy the credit of such an assertion; add to this, that Mr. Boyle's 

 candour and probity stand too well attested, to leave the slightest suspicion that he would have con- 

 cealed such a circumstance, had it been true. But to remove all doubt on this subject, we shall insert 

 the account of this transaction in Mr. Boyle's own words : " After Mr. Kraaft had shown me (says 

 this distinguished philosopher) both his liquid and consistent phosphorus ; being by the phaenomena 

 I then observed made certain, that there is really such a factitious body to be made as would shine in 

 the dark, without having been before illumined by any lucid substance, and without being hot as to 

 sense ; I considered in what way it might be most probable to produce, by art, suchashiningsubstance. 

 Mr. Kraaft indeed gave me, in return of a secret I communicated to him, a remote hint of the 

 principal matter of his phosphori, by saying it was somewhat that belonged to the body ot man.— 

 But I made many fruitless attempts, with many unlucky accidents, before 1 could bring the thing to 



