38 ESSAYS AnD OBSERVATIONS 
adjoining to it on the upper fide a very 
faint ftream of gfeen and blue. White 
bodies illuminated with it, appear alfo 
thro’ the prifm perfectly well defined ; 
both which are very furprizing phenomena 
to thofe who have been accuftomed to the 
ufe of the prifm in other heterogeneous 
lights, where it never fails to throw con- 
fufion on the extremities of all vifible ob= 
jects. 
29. Because the hole appears thro’ 
the prifm quite circular and uniform in 
colour, the bright yellow, which prevails 
fo much over the other colours, muft be 
of one determined degree of refrangibili- 
ty; and the tranfition from it to the faint- 
er colour adjoining, not gradual, but im- 
mediate. 
30- UPON examining foap-water-films 
in the fame light, I could only obferve 
luminous bands feparated by dark ones; 
the green and blue being too weak to af- 
fect my eye in this view. It would be 
needlefs labour to enter here into a parti- 
cular detail of the reafons of the different 
transformations of coloured bodies, above 
related 
