C 194 ) 
crofs the Space between the Two, and interfefted the 
Secondary, as in the Figure AFCG. interfedts the Se- 
condary Iru EF6D, dividing the Arch ED into Three 
equal Parts, as near as I could then guels: but at firft 
the Arch AF did not appear, which atterwards became 
as bright as the former, lobferved the Points /^and G to 
arifeand the Arch gradually to contradjtill at length 
the Two Arches FHG, ^nd FG became co-incident ; 
when for a great Space, the Secondary Iris loft its Co- 
lours, and appeared like a White Arch at the Top. I 
obferved alfo, that at the Points F and G, the Inter- 
ftftion of the Interior Red of the fecondary Iris^ and 
the exterior Red of the Arch, was much more inrenfeJy 
Red than the outward Limb of the Primary Iris; and 
that during the whole Appearance, the upper Part of 
the third /r/j was not at all vifible, beyond the Interfe- 
ftions, (j. This uncommon Sight entertained me for 
about Twenty Minutes , when the Clouds blowing away, 
the whole Vaniflied. I was at firft amazed with the 
Sight, but afterwards, recolleding that the Sun /hone 
along the River Dee^ which from thence empties it (elf 
into the W.NW. where the Sun then was, I concluded, 
this Secondary Arch, AFHGC, was produced by the 
Beams of the Sun refleded from that Water, which at 
that time was very Calm ; and it had been much more 
Bright had it been at that time about High, as it was 
Low Water, when ail the Sands were bare. I was foon 
confirmed that my Suppofition was Right, and that it 
anfwered all the Appearance without any Scruple, and 
that the Arch AFHGC , was no other than that part of 
the Circle of the /m, that would have been under the 
Earth, bent upwards by Refi[ec3:ion; of which no more 
need to be faid. I remember not to have read of any 
fuch /m, in any Author I have hitherto met with, and 
though Des Carte Sy in his Meteors ^ pag. 21$. of the 
Amfterdam 
