Reply to a Note in the Amxales de Chimie^ 185 
rescent^ and the blue part opaque^ whereas I observed three dif- 
ferent colours, besides the opaque portion, namely, purple light, 
yellowirsh-green light, and whitish light ; and I venture to say, 
that the sight which I saw has never been described, and is one 
of the most splendid exhibitions of a natural phenomenon that 
can be witnessed. Had not my description of the experiment 
been printed the day after it was made, and when all the Plates 
of the Journal were thrown off, I should have given an engraving 
of it, which would have represented one of the finest patterns 
of the kaleidoscope, drawn with phosphoric light, and displaying , 
the whole crystallographic structure of fluor-spar, — a structure, 
too, which could not be seen either by the nfiked eye, or by the 
aid of a microscope. 
But beside the novelty and splendour of this phenomenon, we 
may claim for it a higher character, as it has led to the deter- 
mination of the only general point which has been ascertained 
respecting the cause of phosphiOrescence, and which we shall be 
able to lay before our readers in a subsequent Number. 
Here we intended to have concluded these remarks ; but it 
naturally occured to us, that as M. Arago had given a garbled 
translation of my notice, by leaving out an important part, 
which tended to overturn his view of the matter, he might also 
have given a false quotation frorn Pallas. I therefore lost no 
time in procuring Pallas’s Memoir, which was published in 1787, 
in the Petersburg Memoirs for 1785, and I found my suspicion 
completely verified 
* In order that the reader may judge for himself, I shall give in this Note 
the whole, of Pallas’s Memoir. 
“ Sa Majeste Imperiale ayant remarque Elle-meme que des echantillons d’un 
spath fluor, recemment envoyes de Catherinenbourg par M. le Gouverneur-Generat 
KaschJcin^ possedent non seulement un degre superieur de la vertu phosphorique 
que Ton connoit a plusieurs especes de fluors, au point de devenir lumineux dans 
I’eau chaude ; mais aussi que la lueur phosphorique qu’ils repandent a une chaleur 
plus forte passe d’un verd seladon au plus beau bleu de turquoise, phenomene que 
les fluors connus n’offrent pas : cette Grande Souveraine, toujours attentive a 
I’avancement des Sciences & gracieusement disposee envers Son Academie, m’a 
charge de remetti*e a la Conference un bel echantillon de ce fluor nouvellement de- 
couvert, avec plusieurs petits, qui peuvent servir aux experiences. 
“ Le grand echantillon, destine pour le cabinet academique, montre clairement, 
que ce fluor s’est trouve en filon, de la largeur d’une main, dans une gangue mi- 
cacee dont Ics deux salbandes montrent des restes. La coiUeur de la plus grand§ 
