Of Light and Colours. 389

but on the contrary seem rather to approve of it, asSir Isaac in his Optics , and Or. Smith in his, hasadopted the fame entirely ; I think upon thele Accounts,and considering the Character of the great Author, theReader will be pleased to have the fame in a very con-cise Manner represented to him.

5. His Pojlulatum is, That there' are certain Globulesin the Atmosphere consisting os a Goat or Shell os transparentJce or Water , containing an opake Nucleus or Kernel with-in ; and that these are made from Particles of Snow,

(which is in itself opake) attracting the aqueous Par-ticles in the Vapour or Exhalation by which it is sus-tained, which gathering together form the pellucid Shellof Water, or are frozen into a crystalline Shell of Ice jand this he thinks is proved to be Matter of Fact by theHail-stones which fall to the Earth, for these (says he)when broken do discover some Snow at the Centre.

6. These Things premised, he addresses himself tothe Solution as follows : Let ABCD represent such aGlobule, with the opake Nucleus E F in the Middle of Plate

it; and let us suppose the Rays coming from G, H, to XLIV-fall on the Side AD. It is manifest they will be re- Fig. 4,fracted inwards from the Surface A D ; from whence itfollows, that a great Number of them must strike uponthe Kernel E F.

7. Let G A and HD be the Rays which after Re-fraction touch the Sides of the Kernel E F, and letthem be refracted again at B and C, emerging in theLines B K, C K, crossing each other in the Point K,whose Distance from the Globule is somewhat less thanits Semidiameter.

8. Wherefore, If B K and D K be produced towardsM and L, it follows that no Light coming from theSun through the Globule can proceed to the Eye anywhere placed within the Angle L K M, or rather in theCone which that represents, supposing that the Obli-quity of the Incident Rays H D and G A is such asshall make the Arch Q_C and Q__B the greatest possible ;

(seethe last Note, Art. 5.) for then all the Rays exte-rior to H D, G A, will be refracted nearer to Q_, andafter Emergence cross each other in a Point k nearer theGlobule than the former, and therefore cannot come atthe Eye placed within the said Cone L K M.

9. Sup-