( 23 ° ) 
f. That the Colours took up lefs Space, and were 
much more lively in thofe Parts of the Iris that were 
near us, than in thofe at a Diftance. 
Thefe Phenomena may eafily be accounted for, by 
comparing this Iris D C E, Fig. 2. with the common 
Iris k i E e form’d by Drops falling in the Air at a 
fmall Diftance from the Eye of the Spectator, H, and 
touching the Ground with the lower Part of its Arch 
in E, the vertical Point of the Iris D C E. Produce 
the Cone H k i E e : Its Interfedion with the Plane 
of the Horizon will give the Figure of the Iris DCE. 
Hence it follows, 
i ft. That as the Angle e H G happens to be greater, 
equal to, or lefs than 90 deg. the Figure will be 
an Hyperbola , Parabola , or Ellipfis. 
2. That as the Sun was about 30 deg. high, when we 
view’d the Ph^fiomena, the Iris was an Hyperbola. 
3. That the Arches of the fame Iris , confifting of 
Colours of different Refrangibility, may alfo in lome 
Cafes be different Sedions of the Cone. 
4. That fincethe Angle e H F is always given ,* from 
the Height of the Point of View H G, and the Sun’s 
Altitude S L A, the Dimenfions of thefe Iris's arc 
eafily determin’d. 
V 
I arrty &c. 
4 
* 
Ben. Langwith. 
% • ' . . „ * 
IX. Ep: 
