to Heat and Illumhiate Ohjeils. 31^ 



^Jtnd fome faint ones. — O. Brighter than before, and more 

 points vifible ; very diftinft. — Y. Much brighter than before, 

 and more points and lines vifible; very diftinft. — G. Full a§ 

 bright, and as many points vifible ; very difl:in£t. — B. Much 

 iefs bright; very diftinA. — /. Still lefs bright; very diftiuft. 

 1 — v. Much Icfs bright again; very diftinft. 



6th Experifnent. I viewed a guirjea at 9 feet 6 inches from 

 \he prifm, and adjufled the place of the object in the feveral 

 pays by the fiiadow of thp guinea; if this be not done, de- 

 ceptions will take place. — R. Four remarkable points ; very 

 diftinft. — 0. Better illuminated; very diftinft, — F. Still 

 better illuminated ; very difiinft. The points all over the field 

 of view are coloured ; fonie greeri, fome red, fome yellow, and 

 fome white encircled with black about thpm ; between yel- 

 low and green is the maximum of illumination. Extremely 

 dlftin£t. — G. As well illuminated as the yellow ; very dif- 

 tinft. — B. Much inferior in illumination; very difiinft. — ; 

 /. Badly illuminated; dKlinft.rrr-F. Very badly illuminated: 

 J can hardly fee the obje6l at all. 



yt/j Experiment. The nail again at 8 feet from the prifm. 

 — i?. I attended to two bright points, with faint ones be- 

 tween them ; almod all the points in the field of view 

 are red; very diftinft.— 0. I fee all the points better; 

 they are red, green, yellow, and whitifti, with black about 

 them; very dilHnft.— F. I fee better; more bright points 

 and more faint oncs^ the points are of various colours ; very 

 didincl. — G. I fee as well ; the points are moftly green and 

 brightifli-green, inclining to white; very diftin6l. — B. Much 

 worfc illuminated ; very diftinft. — I. Badly illuminated ) 

 Tery diftinct. — r. TJiere is hardly any illumination. 



Htb Experiment. The nail again at 9 feet 6 inches from 

 the prifm, by way of having the rays better feparated. — 

 R. Badly illuminated ; the bright points are very diftinft. — 

 O. Much better illuminated; the bright points very difiinft. 

 Y. Still better illuminated; all points extremely diftinft. — . 

 G. As well illuminated, and equally diftinft, — B. Badly 

 illuminated ; the brij^ht points are diftinit, but the others 

 are not fo. — /. Very badly illuminated; 5 do not fee dif- 

 ^jnftly; but I believe it to be for want of light. — F. So badly 



jlluniinatc4 



