C3®4) 
indeed that very Comet j which he faw with his naked Eye’ and 
©Merged with his geometrical Inftruments, the faid 12, 13, and 
14. dayes of February ^ or whether it was another, and whether he 
had loft that Comet , which moved towards the Second Star in Aries 
hut leaves it to the Learned World, and particularly to th c Royal So- 
tiety, after they (hall have well examined and confidered all his Obfer- 
vations, and the Calculus raifed therefrom , to judge of this, and 
the other particulars in controverfie. 
II. Jfaactts Vojfius de N I L I et A L 10 R.ZS M F LV* 
MIN V M ORIGIN E. It was Numb. 14. of thefe Tranf- 
actions , that gave an account of the Caufe of the Inundation of the Nile , 
as it was rendred by Monlieur de la Chamkfe : This is to give you 
another, not only of the Inundation, but alfo of the Origine of that, 
and of other Rivers , as it is delivered by Monlieur Ifaac VoffuiS) 
who undertakes in this Book to (hew • 
1. That thofe Subterraneous Channels , through, which feveraf 
■ Philofopkers teach, that the Sea di [charges it (elf into the Rivers, 
are not only imaginary, but ufelefs, in regard *tis impofsible for the 
water to. rife from the Subterraneous places up to the Mountains, where 
•ommonly the Sources of Rivers are. 
2. He explicates, why, if a Pipe be put into a Bafon full of Wa- 
ter , the water is feen more raifed in the Pipe, than in theBa- 
fon and rifes higher according as the Pipe is narrower ^ On the 
contrary, if the fame Pipe be put into a B?.fon full of Quickfilver 5 
the Qaickfilver ftayes lower in the Pipe , than in the Bafon. The 
jeafon , which he renders hereof , is That as the Water fticks ea- 
fily to all it touches, it is fuftain’d by the fides of the narrow Pipe 
wherein it is included : And indeed, if the pipe be quite drawn out 
of the Water, the Water doth not all fall out, but fo much of k 
remains-, as the Tides of the Pipe could luftaine : Whence it is, that 
the Water which is kept op by the Walls of the Tube , weighing 
no longer upon that which is in the Bafon, is thruft upwards, asd . 
keeps it felf raifeth^bove its Levell ^ but the QuickGlver not ad- 
hering fo eafily, as Water, to Bodies it touches , is not fuftained by 
chp Tides of the Tube, and fo mounts not above its Levell , bue 
rather defcends below it , becaufe the Pipe, which is ftreight, hin- 
ders the endeavor that is in the Mercury to rife to its Level. He 
adds, that this Observation makes nothing for the Explication of. 
