332 Prof. Necker's Observatmis on some remarkable 



From the combination of all these circumstances, it remains 

 not unlikely? nay, even probable, tliat icy particles may have 

 been floating in those light mists which gave rise to the par- 

 helia, if we suppose their height to exceed a good deal that 

 of 1000 toises above Geneva, or 1280 toises above the level 

 of the sea. 



Although mistaken in my former statement of the epoch on 

 which the parhelia took place, considering that June, though 

 not the hottest, as I said of July, is at least a hot month of 

 our summer, that the occurrence of a parhelion in that season, 

 and in such a latitude as ours (46'' 12' N. lat.), is a very rare 

 thing, and that by the knowledge we have been able to get of 

 the meteorological circumstances attending such a phaeno- 

 menon (circumstances which I do not believe have been men- 

 tioned in similar accounts of parhelia), — we are able to form an 

 idea at least of the minimum of height at which the refracting 

 medium causing the parhelia must have been placed. I do 

 not regret to have drawn your attention to this fact, which, 

 instead of militating against, will rather tend to corroborate 

 your ideas as to the necessity of supposing minute crystals of 

 ice to explain the phajnomenon. 



I now come to the point which you particularly wished me 

 to describe to you : I mean the luminous appearance of trees, 

 shrubs and birds when seen from the foot of a mountain, a 

 little before sun-rise. The wish I had to see again the phae- 

 nomenon before attempting to describe it, made me detain this 

 letter, a few days, till I had a fine day to go to see it at the 

 Mont Saleve ; so yesterday I went there and studied the fact, 

 in elucidation of which I made a little drawing, of which I give 

 you here a copy: it will, with the explanation and the annexed 

 diagram, impart to you, 1 hope, a correct idea of the phjenome- 

 non. You must conceive the observer placed at the foot of a 

 hill interposed between him and the place where the sun is 

 rising, and thus entirely in the shade ; the upper margin of the 

 mountain is covered with woods, or detached trees and shrubs, 

 which are projected as dark objects upon a very bright and 

 clear sky, except at the very place where the sun is just going 

 to rise ; lor there all the trees and shrubs bordering the mar- 

 gin are entirely, branches, leaves, stem, and all, of a pure 

 and brilliant white, appearing extremely bright and luminous, 

 although projected on a most brilliant and luminous sky, as 

 that part of it which surrounds the sun always is. All the mi- 

 nutest details, leaves, twigs, &c, are most delicately pi'eserved, 

 and you would fancy you saw these trees and forests made of 

 the purest silver, with all the skill of the most expert work- 

 man. The swallows and other birds flying in those parti- 



