Microcrapuya. 
- more then A; fothat from F to A, there is @ continual mereale of heat, 
and confequently of rarity 5 from whence it will neceflarily follow, that 
the Rays of light will be infle@ted or refracted in it, in the fame man- 
ner as they would beina Concave-glafe , for the Rays GKI, G K I will 
be inflected by GK H, GK H, whichwill eafily follow from whatI be- 
fore explained concerning the inflection of the Atmofphere.. 
On the other fide, a defcending vapour,or any part of the air included 
__ byan afcending vapour,will exhibit the fame efle@s with a Convex lens j 
_* for,if we fuppofe,in the former F igure,the quite contrary conftitution ta 
~ that laft defcrib’d 5 that is,’ theambient Air’ FF bemg hotter then any 
_ partof that matter within any circle, therefore the coldeft part mult 
_neceiflarily be A, as, being fartheft remov'd from. the heat , all the 
intermediate: {paces will be gradually difcriminated by the continuall 
mixture of heat and cold, fo that it will be heétter at E E, then DD, in 
_ DDthen CC, inCC thenBB,andin BB then A. From which, a like — 
refraction and condenfation will follow; and confequently a lefler or 
greater refraction, fo that every included part will refraét more then the 
- including, by which means the Rays, GK I, G K I, coming {rom a Starr, 
or fome remote ObjeG, are fo inflected, that they will again concurr and 
micet, in the point M._ By the interpofition therefore of this defcending 
vapour the vifible body of the Star, or other Objet, is very much aug- 
mented, as by the former it was diminifhed. — - 1 3 
_ From the quick confecutions of thefe two,one after another, between 
the Object and your eye,caufed by their motion upwards or downwards, 
_ proceeding from their levity or gravity, or to the right or left;proceed=_ 
ing from the wind, a Starr may appear, now bigger, now lefs, then really — 
__. it would otherwife without them; and this is that property of a Starr, 
whichis commonly call'd twinkling, or {cintillation. pan 
The reafon why a Star will now appearof one colour,now of another, 
which for the moft part happens when ‘tis neer the Horizon, may very 
eafily be deduc'd from its appearing now in the middle of the vapo 
other whiles neer the edges for if you look againft the body of a Starr 
with a Zele/cope that has a pretty deep Convex Eye-glafs, and fo order it, 
that the fis may poeear eas in one place,and {ometimies in another 
of it;you may perceive this or that particular colour to be predominant 
in the apparent Figure of the Starr, according asitis more or lefs remoté 
from the middle of the Lezs. This I had here further explain’d, but that 
it does more properly belong'to another placee 6 
vital sadetewec ies add fome few Queries, which the confideration 
of thefe particulars hinted, and fo finifh this Section, 
~ And “a firftI fhall propound is, Whether there may notbe a 
artificial tranfparent body of an exact Globular Figure that fhall fo 
infle& or refraé all the Rays, that,coming from one point, fall bi cepa 
Hemifphere of it; that every one of them may theet on the oppo , ides 
_and crofs one another exactly in a points and that it may do the li of 
__ withall the Rays that, coming from a Jateral point, fall upon any oe 
_- Yemtifphere; for if fo, there were to be twpee a perfection of omen ; 
* 
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