LIB. II. 36. 247 



ex priscis philosophis opinati sunt; an solida et densa, 

 ut Gilbertus et multi moderni, cum nonnullis ex anti- 

 quis, tenent. Rationes posterioris istius opinionis ftui- 

 dantur in hoc maxime, quod lima radios solis reflectat ; 

 neque videtur fieri reflexio lucis nisi a solidis. 



Itaque instantice crucis circa hoc subjectum ea? esse 

 poterunt (si modo aliquaf: sint) quee demonstrent refle- 

 xionem a corpore tenui, qualis cst flamma, modo sit 

 crassitiei sufficientis. Certe causa crepusculi, inter 

 alias, est reflexio radiorum solis a superiore parte 

 aeris 17 . Etiam quandoque reflect! videmus radios solis 

 temporibus vespertinis serenis, a fimbriis nubium rosci- 

 darnm, non minori splendore, sed potius illustriori, et 

 inagis glorioso, quam qui redditur a corpore lunoc ; 

 neque tamen constat, eas nubes coaluisse in corpus 

 densum aqua?. Etiam videmus, aerem tenebrosum 

 pone fenestras noctu reflectere hicem candelse, non 

 minus quam corpus densum I8 . Tentanduin etiam foret 

 experimentum immissionis radiorum solis per foramen, 

 super flammam aliquam subfuscam et caeruleam. Sane 

 radii aperti solis, incidentes in flammas obscnriores, 

 videntur eas quasi mortificare, ut conspiciantur magis 

 instar fumi albi, quam flammsc. Atque hocc imprcesen- 

 tiarum occurrunt, qua? sint ex natura instantiarum cru 

 cis circa hanc rein ; et meliora fortasse reperiri possunt. 

 Hed notandum semper est, reflexionem a flamma non 



and the new school. Their proof of so that the fact of &quot; Reflexio a cor- 



its solidity was not of much value, pore tenui&quot; is fully established. 



Bvit this signifies little now that we 18 Bacon s reason for this pheno- 



are able to calculate accurately the menon is wrong. It is really the 



density, not only of the Moon, but polished surface of the glass which 



even of the most distant Planets. reflects the rays : and this is always 



!? True enough, if we add the the case, but is only visible to us 



Refraction of rays. The blueness when there is neither light nor ob- 



of the air arises from the watery ject on the other side to destroy 



particles in it: and the light thus the image created, 

 reflected from the sky is polarised : 



