Scientijic Intelligence. — Meteorology . 209 



ilia, will but seldom appear. I attribute these colours to the 

 interference of the i-ays which have traversed the vesicles of 

 ^vater or vapour, with those which have traversed air only. 

 The phenomenon simply implies, that the part of each tra- 

 versed vesicle is not too thick, a supposition which is easily 

 admitted a priori. It is completely of the same nature with 

 that which you have yourself observed in mica or gypsum 

 plates of different thicknesses, and in which the two neigh- 

 bouring rays which traverse the different thicknesses of the 

 mica or gypsum interfere, and so produce the coloured r^s 

 (an experiment which, in a parenthesis, we may observe, has 

 trtice been reimported during the last year fi'om England) ; 

 they are likewise the phenomena known under the term of the 

 mixed plates of Dr Young. To produce, then, a blue sun, the 

 red, yellow, and even the violet sun, I have taken (see Societe 

 Philomatique, 1827) two plane circular glasses, separated by a 

 layer of mixed water and air, of oil and air, and, finally, of oil 

 and water ; and by suitably approximating the glasses, I have 

 made the flame of a lamp to be seen through them of a uniform 

 red tint, and of a blue and violet tint, at pleasure. The en- 

 feebled image of the sun reflected by water assumes the same 

 colours ; and the moon still more strikingly, and by du-ect vision. 

 Hence, then, I imagine nothing requires to be added to the 

 explanation and the reproduction of the meteorological phe- 

 nomenon. — 'Not, however, to dismiss the subject of the colours 

 of mixed platen, without pointing out some other particulars 

 besides their very uniform tints, I shall remark, that around 

 the flame may be perceived the field of two glasses of a more 

 feeble colour, and complementary to the colour of the flame ; 

 a circumstance of which Dr Young, whom I consulted upon it, 

 could not perceive the cause which I have somewhat investi- 

 gated. I still contend, that these colours differ from the usual 

 colours of their plates, in that these latter, in the oblique in- 

 cidences, are polarized in the plane of incidence, both as it 

 respects the transmitted rays and the reflected rays, as you 

 have demonstrated in the Memoires d' Arcueil ; a circumstance 

 which does not occur in those colours of mixed plates, which 

 are transmitted obliquely, and which are partially polarized 



VOL. XXVII. NO. LIII. JULY 1839. o 



