(2C48) 
fome cafe be not fuch. The other is, that it day be fappofed, 
that half the light or appearance, diffufed from the Objeft, is 
refracfted according to the Vjual Refra&ion 5 but the other 
half according to the 'L?^-;^^/ Refraftion ; or, which is all 
one, that the Ufual and Un-ufual Refradion have the fame 
power to refrad the Rays of the Objefts^The former of thele 
SuppofitiGnshecolleflrsfrom Exper» i4 5the latter from Exp* 
8* Butj how he proceeds in thefe DecluHions, and the there- 
on grounded Demon^rations^ may be more fully and more 
plainly fecn in the above-mentioned Tr^S it felf, than can be 
conveniently deliver'd in this Efitome^ 
An Extract of d Letter from a LearTjed Frefjch Gentleman ^ 
concerning a roay of making Sea-water fipeet, 
MOnfieur Hanfon hath now declared his fecret of 
making Sea water fweet* It confifts frji in a Pre- 
cipitathn^ made with Oyl of Tartar^which he knows to draw 
with fmalJ charges. Next^h^ dijiilh the Sea- water 5 in which 
work the Furnace taketh up but little room, and is fo made, 
that with a very little wood or coal he can diftilJ 24 pots of 
water in a day ; For the cooling of which, he hath this new 
invention, that inftead of making the Worm pafs through a 
Veflel full of water (as is the ordinary praftife^) he maketh it 
pafs through one hole^ madeon purpofeoutoftheShip, and 
to enter in again through another : So that the Water of the 
Sea performeth the cooling part.- By which means hefaveth 
the room , which the common Refrigerinm would take up • 
as alfo the labour of changing the Water 5 when the IVorm 
hath heated it* But then thirdly^ he joyns the two precedent 
Operations^F/V/r/^Z/i^^jthereby perfectly tocorreft the malig- 
nity of the W ater.This Filtration is made by means of a pecu- 
liar Earth, which he mixeth and ftirrs with the diftilled watei'^ 
and at length fujEfers to fettle at the bottom, Paris Febr* 2 2. 
An 
